This section contains special information on the Electrical Systems that is not found in the Service or the Bentley manuals.

All information contained in this FAQ is provided by BMW enthusiasts who are not typically fully trained in the art of BMW maintenance. As such, all information in this FAQ is provided "as-is". Any use of this information is strictly the responsibility of the using party. The supplier of the information and the Webmeister assume no liability for incorrect information or use of this information.


Windshield Washer Tank Level Sensor Repair

One Touch Power Windows

Fuse Designations - '84 633

Fuse Box Wire Colors & C1 Connector - 1983 633

External Temperature Sensor (DIY) Summary

OBC Not Working - Internal Fuse Replacement

SRS Warning Light Reset

Remote SI Board Battery Holder

Instrument Panel Lighting Improvement

Replacing Alternator Brushes

On Board Computer (OBC) Differences

OBC Display Bulb Replacement

Convert OBC to LED

OBC Touch Pad Bulb Replacement

Interior Light Timer Control Module Repair

Radio Backlighting Fix

Radio (After-Market) Install

After-Market Radio Install (another input)

Converting from a Four Filament Headlamp System to a Six Filament System

Three Different Headlamp Wiring Configurations Used on US 6 Series

Electrical Relay Information and Replacement Guide (1983 through 1989 Models)

General Headlamp Information


Windshield Washer Tank Level Sensor Repair - "Legros, Phil" <legrosp@akcity.govt.nz>

The level sensor works through a magnetic ring in the float triggering a reed switch inside the stalk of the level sensor. If the connection to the reed switch corrodes through because moisture has got into the unit or the switch itself goes AWOL, the level sensor will either indicate empty at all times (open circuited) or full at all times (switch staying closed even when the float (magnet) moves down with falling water level. The same principle may also apply to the coolant level sensors - haven't checked this out. Repair is simple. Typing this up took longer than fixing mine with new reed switch.


Lift the unit off the washer tank. Close inspection of the cap of the unit shows an inner central piece (with the spade clip lugs on it) that is "clipped" into the cap that fits the tank. Wriggling the spade lug mounting relative to the cap lets you see where the two bits are joined. It is retained in place by a circular lip formed in the plastic cap which can be eased back with a small screwdriver. The plastic is relatively stiff and may break out a small piece. Don't worry it can be sealed up later. When the retaining lip is lifted slightly the inner piece can be levered out (mine flicked out and flew across the workshop!!) past the lip.


Once out; you will see that the inner piece is simply a plastic tube (under the moulding with spade lugs on it) with one wire going down its centre and another running down the side of it, The reed switch solders to the ends of these two wires completing the circuit between the two spade lugs at the top of the sensor. The switches lies vertically alongside the tube so that it is "surrounded" by the magnet in the top of the float when the float is in its full position.

Inspect the reed switch and its connections to see where the fault is. You should get closed circuit when the magnet in the float is held near the reed switch. Open circuit means either the switch is faulty and isn't closing when the magnet is adjacent to it or there is a broken (corroded) wire. If the closed circuit tests OK you should try for an open circuit when the magnet is moved away from the switch. If the circuit stays closed it indicates that the reed switch is faulty & is not opening when the magnet moves away from it.

Replacement glass enclosed miniature reed switches (normally open type) are available from electronics stores for about $2 -$3. Soldering a new switch in is straightforward. Broken connections to the switch can be resoldered. If the wires have broken internally fixing them could require more dissecting of the unit which might be more trouble than getting a replacement from a scrapyard.


Once repaired, the inner piece has to be fitted back into the cap/stalk unit. I filed a small taper on the underside of the flange of the inner piece so I could ease it down into the circular retaining lip on the cap. Gentle squeezing with pliers helped it clip into place: followed by some massaging of the retaining lip back to its undisturbed shape. I put some black silicon sealer around the join between the inner piece and the retaining lip to make it waterproof and to cover up the small piece of the lip that broke out while I was levering.


One Touch Power Windows Don Mies <mies@macsch.com>

Not too LONG ago I had posed the question about one-touch windows for my '87 325isWell a big thank you to who ever posted this URL to Dealer Marketing http://www.dzn.com/global/bmw.htm earlier today because it contained the following in the parts catalogue, it exists!, you can also contact them be phone at 1-800-590-7770

BMW One Touch Power Window Module

Fits all 3, 5 and 6 series 1984 through 1990. A recent option available in most late model BMWs is the one touch express power window feature. By simply touching thepower window button and immediately letting go, the window will travel all the way down on its own. Or, if you retouch the window button the window will stop at thatpoint. You can now have this great feature in your older BMW. Very simple to install. Full written directions completewith photos shows you step by step how to add thispopular option to your older BMW. Estimated installation time is 35 to 45 minutes. All units are pre-tested before packaging. A simplefourwire hook up to your car. Youneed only to cut one wire in your console near the window button to make it operate. A nice option to have. Module size is only 2" x 3" x 1" wide. On the 3 series themodule fits under the console along side the brake handle. On the 5 series and 6 series it can tuck under the side of the console.

Fuse Designations - '84 633 - David Hoerl <dfh@ariel.com>

Apparently, the owner's manual for the '84 633 has incorrect fuse descriptions. What follows is the correct designations. These values are from the Electrical Troubleshooting Manual (ETM) for the 84 633CSi.


Fuse Assignments

Fuse #


1 7.5 Headlights (also fuse fuses 2, 13, 14)
2 7.5 Headlights (also fuse 1, 13, 14)
3 25 Aux Fan
4 15 Lights Turn/Hazard Warning (also fuse 24)
5 25 Wiper/Washer and Washer Heater
6 7.5 Active Check Control (also fuse 10, 12, 21, 22, 23)
Cruise Control (also fuse 17)
7 15 Horn
8 N/A
9 7.5 Idle Speed Control (also fuse 17)
10 7.5 Active Check Control (also fuse 6, 10, 21, 22, 23)
Onboard Computer (also fuse 10, 21, 27)
Speedometer/Gauges/Warning Indicators (also fuse 21)
Brake Lining Warning
Service Interval Indicator (also fuse 21)
11 15 Fuel Delivery
12 7.5 Active Check Control (also fuse 6, 10, 21, 22, 23)
Onboard Computer (also fuse 10, 21, 23)
Radio (also fuse 2, 28, radio inline fuse)
Warning Indicators
13 7.5 Headlights (also fuse 1, 2, 14)
14 7.5 Headlights (also fuse 1, 2, 13)
15 N/A
16 30 Heating and A/C
17 15 Aux Fan
Backup Lights
Cruise Control (also fuse 6)
Lights: Dash/Transmission Range (also fuse 23)
Idle Speed Control (also fuse 4)
Interior Lights (also fuse 21)
Power Mirrors
Seatbelt Warning
18 30 Aux Fan
19 30 Sunroof
20 25 Rear Defogger (also fuse 23)
21 7.5 Active Check Control (also fuse 6, 10, 12, 22, 23)
Auto-charging Flashlight
Gauges (also fuse 12)
Glove Box light
Indicator Lights (also fuse 17)
Onboard Computer (also fuse 12, 27)
Radio (also fuse 12, 28, radio inline fuse)
Service Interval Indicator (also fuse 10)
Trunk Light
22 7.5 Active Check Control (also fuse 6, 10, 12, 21, 23)
Lights: Front Park, Ras[???] (also fuse 20)
23 7.5 Active Check Control (also fuse 6, 10, 12, 21, 22)
Rear Defogger (also fuse 20)
Lights: Front Park/Tail/Under Hood (also fuse 22)
Lights: Visor/Dash (also fuse 17)
Lights: Rear Marker/License
24 15 Ignition Key Warning
Lights: Turn/Hazard Warning (also fuse 4)
25 25 Power Distribution
26 25 Power Seats
27 25 Control Locking
Heated Door Locks
Onboard Computer (also fuse 10, 21, 22)
28 25 Cigar Lighter
Power Antenna (also fuse 12, 21, radio inline fuse)
29 7.5 Fog Lights (also fuse 30)
30 7.5 Fog Lights (also fuse 29)


1983 633 Fuse Box Wire Colors & C1 Connector - "Gene M." <MClan@postoffice.worldnet.att.net>

On electrical issues on the 6 series, you may not want to assume that all information in schematics, repair manuals or the Electronic Troubleshooting Manuals are correct. Even basic wire colors from the fuse box may vary from the printed information. If you are tracing a major electrical problem, you may want to first confirm the wire colors coming from the fuse box against your printed material. (The 7 series service manual was consulted because the schematic showed its application for both the 83 733 and 83 633.)

(If fiche & 7 series manual agree with actual --no entry)
8 N/A
10 GN/WT
11 GN/VI
12 VI/WT
13 YL/WT
14 YL/BU
15 N/A
16 GN/BR
17 GN/BK
19 GN/RD
21 RD/GN
22 GY/BK
23 GY/GN
24 RD/WT
28 RD/YL
29 YL/BR
30 YL/VI


C1 connector Pin 4 (Blue 26 pins on back of instrument cluster)

Actual RD/BK fuse 27 Printed material RD/GN fuse 21



External Temperature Sensor (DIY) Summary - lxh21@psu.edu (Louis P. Hodgson)

Finally this afternoon, I went ahead to assemble all of the components together.

I purchased the following:

1) NTC thermistor (5k ohm@25C) KC005N-ND (from Digi-key) $2.72

2) 200k ohm potentiometer 3329H-204-ND (from Digi-key) $2.01

3) heat shrink tubes of various diameters (Radioshack)

4) Project box (plastic box of 1"x 1.5"x 3" to put the resistor assembly in) (Radioshack)

5) 47k ohm fixed resistor (Radioshack) $ 0.49

6) Wires (couple of different colours) and the original connector from my car

7) 1/4 inch copper tubing (hardware store, under "Plumbing" section) $1.87

8) Lot's of solder.

Now the procedure:

1) First construct the temperature probe: I took the 1/4" copper tubing (a little too flexible, but has great heat trasfer characteristics. could also use brass,... or silver/gold!), cut it in about 3 inch section. I filled one end of it with solder so as to make a good plug. Sand off excess solder to make it nice and rounded. Next, take the thermistor, it's legs are not insulated... I placed the insulation material pulled off of comparable diameter wires on each of the legs so as to insulate them. I soldered on wires of about a foot in length to each of the legs, put heat-shrink tube around the connection for insulation. Insert the thermistor into the prepared copper tube. Take note that it would be a good idea to take a heat-shrink tube of slightly less diameter (as compared to the copper tube) and insert it into the tube all the way before inserting the thermistor. This will insulate (electrically) the tip from short-circuiting by touching the bare metal. (heat shrink tube will not pose much problems to heat transfer). Once the thermistor is inserted all the way, take a heat shrink tube that's greater than the diameter of the copper tube and use that to seal off the tail-end. (I wish I took pictures...) Now you have a nice temperature probe that's insulated and protected from moisture!

2) Electrical connection: Essentially, what you have to do is to connect the thermistor probe constructed in (1) to the potentiometer and then to the car in parallel. The ideal resistance that one should connect the thermistor to is 220k ohms. But, no one makes such a potentiometer... So, I took the 200k ohm potentiometer and connected a 47k ohm fixed resistor in series. This will produce UP TO 247k ohm resistance (this particular potentiometer listed above will let you adjust the resistance from 0 to 200k ohms using a little screw knob). In retrospect, I would have used a fixed resistor of 100k ohms because it turned out that it needed a lot more resistance to calibrate at 32F. Anycase, connect the thermistor probe, the potentiometer/resistor unit and the connection to the car in PARALLEL connection! The whole wire connection assembly should be carefully insulated and placed in a plastic box and sealed with some waterproof tape of some kind. (I put my box behind the front airdam so I didn't bother waterproofing it)

3) Mounting and adjustment: Take a beaker of crushed ice/water mixture. Make sure it's very cold. Ice needs to be crushed, like frozen Margarita. Dip the probe into it and wait a few seconds before it comes to steady-state. At this time, the car's OBC should read like 33~36F and you should hear a bong. Rotate the knob on the potentiometer (increase the resistance) until the OBC reads 32~33F. I used a couple of calibrated thermometers to measure the actual temperature of ice/water mixture... it turns out to be 0.5 C which translates to 32.9 F. 33F should be good enough. I had to crank up the potentiometer all the way to 200kohm setting (so my total resistance that's in parallel with the thermistor is 247k ohms). I secured the probe on the airdam using a couple of nylon zip-ties, and secured the box onto the back of the airdam where a bracket came down for support, again, using a coupl of zip-ties. I went for a spin, the probe was stable at ~61F. It seems to be a little more sensitive than the factory probe and it has no problems equilibrating quickly even with all the insulation that went into the probe.

If you have any questions, please let me know and I'll try to clarify things better.

Digi-key : http: www.digikey.com They charge extra $5 for orders less than $25... So for the thermistor and the potentiometer came to $4.73 and I had to pay $5 on top of it. The plastic box was $2, resistor was $0.49, wires/heat-shrink tubes/solder/copper tubing <$10. So total was less than $20. Compare that to $74 factory replacement...


OBC Not Working - Internal Fuse Replacement - Michael Osborne <mwosborne@iname.com>

This FAQ explains how to replace the internal fuse of the control modulethat controls the on-board-computer (OBC). This procedure is for an '85635 CSiA Euro Spec car although I suspect that other models are the same.The OBC in this car has the 0 - 9 on the keys. NOT the 1000, 100, 10, 1keys. The OBC not covered by this FAQ may use a similar procedure. Youmay want to follow other trouble shooting procedures first, ie main fusesin fuse box, OBC backlight, OBC relay (located under LH side of dash), andmain relay (located outside of fuse box).

The internal fuse in the control module for the OBC can possibly be blownwhen jump starting the car. The Bentley's manual makes refference to this. Bentley's indicates that you should remove the fuses in the fuse box thatprovide power to the OBC before you jump start your car. I suspect thatjump starting my car is what blew the internal fuse in the first palce.

Replacing the internal fuse in the control module is very inexpensive andonly requires a small fuse and your labor to remove the control module.You may want to follow this procedure first if you are unable to check theother relays and will just replace them. The fuse required for thisprocedure is far less expensive then the other relays and takes less effortto replace than the backlight. If your problem is only the backlight youshould still be able to see the display if the lighting is right (someonecorrect me if I am wrong, I have never gone through the procedure toreplace the backlight).

Now to the procedure:

1. First you may want to disconnect the battary (I did not, but should have).

2. You need to remove the pannel under the steering wheel. This involvesremoving four phillips head screws, disconnecting the wires to the windowbreaker, disconnecting the wires to the temp. sensor for the HVAC system,and removing the vacuum hose to the temp. sensor.

3. The control module is located just to the left of the steering wheeland has two wire harness plugs connected to it. Both are on the front ofthe module, one to the left one to the right. The BMW part number startswith 65 I think. One of the plugs has one large gray cable comming fromit. The other plug has multiple single wires comming from it. These plugsneed to be unplugged. These plugs are wedged in meaning that you separateone end of the plug from the module and the other end of the plug is wedgedin the module. Two 8mm bolts hold the module in place. They can beremoved with a nut driver if need be. Remove the module and take to cleanwork bench.

4. Make sure you have grounded youself well or are wearing a static strapon your wrist and are gounded. Remove the code plug from the top of the unit. It just pullsout. The module is made up of a casing that is solid and surrounds thecircuit boards which are attatch to where the plugs are. The plugconnections and the circuit boards pull out of the casing. Use two smallflat blade screw drivers and pry the casing away from the plug end of themodule. This needs to be done on both sides at the same time so that theboards can be removed from the casing (you will see this when you get tothis point).

5. Now that you have the boards and plug connections separated from thecasing you should be able to look between the two boards near the outsideedge and see a fuse. This is a .5 Amp, 250 Volt, fast acting fuse, lengthof .75 inches and diamater of .375 inches (Radio Shack, $1.99 for four).Use a pair of needle nose pliars and remove the fuse.

6. Replace the fuse and put it all back together. Make sure you installthe casing so that the hole for the code plug in the casing is over theconnection in the circit board for the code plug.

The whole job can be done in about 30 minutes. When you restore power tothe car the OBC should be flashing 4 "." If you need help with thefunctions of the OBC send me email. I have a copy of this part of themanual in English.

As usual, the author of this FAQ can not be held liable for the accuracy oroutcome of using this procedure.

Michael Osborne

'85 635 CSiA Euro

BMW CCA # 113941


How to correct and extinguish the SRS warning light on an 88/89 635 with airbag

If your SRS light comes on and stays on you may want to try this fix. Note that the SRS light is supposed do come on during the first 30 seconds after starting the engine, and then it is supposed to extinguish. I found that if I disconnect and reconnect the harness connectors, I was
able to cure the problem. I found 5 connectors. One on each front fender in the engine compartment -- orange connectors next to an orange box -- and 3 more attached to the SRS brain above the glove box. Be sure that you disconnect the ground lead from the battery before you do any work on the SRS to assure that you do not blow the bag.

In the fiche (maintenance) there is a reference to a diagnostics tool and bunch of diagnostics codes that pinpoint to the trouble section, whether the problem was temporary or permanent. Such a tool is available, but is expensive.

Don Schmidek

SI Board Battery Holder (Wiring Error and Revision) - Bill Wolf (billwolfcarstuff@ixpres.com)

The original article titled "Remote SI Board Battery Holder" contains an important error in the wiring configuration. The following discription corrects that error and profides further clarification on the batteries and the wiring.

The SI batteries are actually two AA size, NiCd, 1.2-volt, approximately 600 or 700 mAh batteries connected in series for a total of 2.4 volts. . Although the original batteries are soldered in place, they contain solder tabs and can be replaced by batteries with similar-type solder tabs. Replacement batteries with solder tabs are also available at Radio Shack (#23-191)(it is a pack of 2 batteries and that is all you need (Mike Gordon). Alternatively, however, the batteries can also be located remotely to the circuit board for easier future replacement. In the older-style instrument panel that was used until January of 1986, the existing batteries are positioned adjacently in opposite directions and the solder tabs are soldered to four individual solder posts. Two of these posts are simply connected to each other by a trace on the back side of the pc board and form the series connection that connects the two batteries. I have not verified the installation configuration of the batteries in the later instrument panel, but they may be the same. Accordingly, remote replacement only requires two wires for connection to a normal (series-configured) double-battery holder. However, because the two batteries are adjacent (rather than end to end), it may not be immediately obvious which end of the pair of batteries has that common connection. Therefore, when wiring with just two wires it is important to identify the end having the common connection and to connect the wires to the terminals on the other end. And, although there is no harm in connecting three wires (or four either) if done correctly, two wires are all that is require.

In the subject article Jim Houts chose to use two individual battery holders. Appropriately then, four wires would have been the more simple and more corresponding configuration for the remote wiring, since it would eliminate having to locate the pair of common terminals. However, the remaining option of connecting three wires has no additional benefit, but still requires the identification of the common terminal pair.

The actual problem in the instructions, however, is that the instructions state to "solder the negative sides of both battery holders to the green wire." And, if this is done literally, it will short one of the batteries when the remaining wires are connected. Also, if the green wire is connected to both negative terminals, then either the red or black wire will also be connected to the green wire at the circuit board terminals because the common terminal posts already connect one positive battery terminal to one negative terminal. I suspect because Jim's installation had apparently worked properly, that it didn't actually follow his own instructions or possibly wrote then after the installation.

In summary, (1) mark the polarity of the existing batteries on the circuit board for reference before removing the old batteries, (2) located the common terminal pair, and then (3) run the wires from the remaining two terminals to the battery holder. Regarding wire colors, red and black are standard designations for positive and negative polarities respectively. Also, if you are in series doubt about having to identify the common terminal pair, then run four different color (or clearly identified) wires to two separate battery holders.


Instrument Panel Lighting Improvement - Gerry O'Connor <BMWCCALA@aol.com>

I have no idea why it took so long for me to address this relatively minor annoyance, but I finally attacked the dim dash light dilemma that's been troubling me for years on my '83 633. One day I began to inspect the dash in order to determine just how much of a job it would be to get the instrument panel removed such that the bulbs could be cleaned/replaced/whatever. Before I knew it, I had the steering wheel off and the i.p. out far enough to remove the two measly little 3 watt bulbs that had been the target of my venom for so long. Popped in a pair of 5 watters, snapped it all back together relatively effortlessly, and voila!...practically enough light to read a map by. An hour or so well spent, in my book. Details follow...

The instrument panel removal procedure is documented in the FAQ at:

Basic items to be removed include the underdash kick and knee panels (which, in retrospect, may not actually need be removed, but it's always nice to seethe center HVAC console, the left side is the check panel) to expose the pod attachment screws (2 screws on each side), the headlight and foglight switch knobs, and the steering wheel (to allow clearance for the pod to be pulled out of the dash). As the I.P. is pulled out, the light sockets for the two light switch indicators on either bottom corner of the I.P. pod will need to be removed as well.
The two OE bulbs located on the top of the pod are bayonnet style single filament bulbs rated at 3 watts and I found Sylvania Part No. 194 to be the same. However, the packaging does not specify the bulb wattage, and I had to peer through the bubble pack to read the wattage off of the bulb. I found another bulb, Sylvania P/N 168, that appeared to be an identical bulb with the exception that the wattage printed on the bulb was '5W' rather than '3W'. (Interestingly enough, the only other difference seemed to be that the package for the 3W bulbs stated 'Made in USA', while that of the 5W bulbs said 'Made in Germany'.)

David Hoerl <dfh@ariel.com> posted that he used a Sylvania/ OSRAM 2825 (5 watt) bulb, but a number of us looked for that bulb in our local auto parts stores with no success. ( I believe the comparable 3 watt version is a 2821, a bulb I also failed to find commonly available.)
I subsequently found a Wagner catalog that had a separate supplement section with detailed bulb specifications, presumably for their entire bulb product line. While it did not list either a 2825 or a 2821, it did include some very helpful info on the 168 and 194 bulbs. It defined both the 168 and 194 bulbs as [T 3 1/4 bulb 13/32 "], showed some dimensioned drawings, and included the following data points (which I've placed in a chart that will hopefully come through legibly):

Bulb # Wattage Amperage Candle Power Rated Avg. Lab Life (Hrs.)
194 3.78 .27 2.00 1500
168 4.90 .35 3.00 2500

bulbs from 3W to 5W, there have been no such reports (mine have been installed for approximately one year and 10,000 miles as of 4/17/98). I promise to dutifully report back, complete with egg on my face, should my dash go up in smoke (or show any signs of meltdown).

Respectfully Submitted,
Gerry O'Connor


Replacing Alternator Brushes - "Don Schmidek" <dis@ricochet.net>

For those who have over 150K miles on their cars and have not had alternator problems, here is a simple preventive action that should save you down-time and significant costs.

Most alternators on German cars fail due to brushes wearing down (as they are supposed to) between 150k and 200K miles. Brush replacement is very easy -- it should not take over 20 min. and the brushes cost just $5.00 for the set.

To replace brushes just remove the regulator assembly -- back of alternator held in place with two Phillips head screws. The has a round transistor mounted on the outside on Bosche alternators -- the other type is similar but uses different brushes. Pop the regulator out, after removing the screws. Note the brushes and the soldered pig tails. I removed the brushes by cutting the top of pigtail right through the solder joint. The brush should just pop out- don't loose the spring - don't let it fly out. Use a ~0.03" drill from the back (the side the brush fits into) to clear out the hole in the eyelet. Insert the lead wire of the brush -- be sure to fit the spring first -- into the brush holder through the hole you drilled --- wrap the brass lead wire to hold the brush so you can solder it in place with the brush protruding about 80+% of it's length - this is very important. After soldering, cut the brass lead wires without cutting into the solder fillet. You will need a 15-30 W. soldering iron.

Fitting the regulator back is simple, but you must install it starting at an angle, to assure that the brushes compress when the regulator is flush with the alternator and the screws are tightened.
You are now ready for an other 200K miles of alternator life.



On Board Computer (OBC) Differences - Joachim Steinle <Joachim.Steinle@bmw.de>

I've been watching the recent discussion on this topic and maybe I can help to avoid some confusion (an ETM is a big help here!):

There are 2 different types of obc on 6ers:

1st gen. obc (till mid '84, 0,...,9-keys and LEDs at the sides): The code relay is integrated into the big metallic control box above the driver's leg room panel. To find and open it, check FAQ (OBC fuse replacement). Wiring is via black connector, input and output wire color both green (if I remember correctly, check ETM)

2nd gen. obc (with 1,10,100,1000-keys): This one only has a small black plastic relay box in addition to the display unit, and there are only 2 relays in it (1 for code, 1 for the alarm horn). It's located also behind the leg room panel, in a common bracket with the cruise control box. There are two plugs attached: 3-pin = input from obc 4-pin = output to main relay/motronic and alarm horn The wire colors for the code in/output are green and green/red. If you have a factory alarm (with the magnetic key), the relay box is integrated in the alarm control unit (same size box, but more addtl. plugs)

Both types: Until 06/87 (Motronic 1.0), the output from the code relay directly triggers the main relay. After that date (with Motronic 1.1), this is just a signal line to the Motronic, which controls the main relay itself depending on the voltage on this line.

The code function can be permanently switched off by directly connecting the code in-/output wires (green and green/red)

General: The code relay is normally closed and opens, when activated. It is activated only when Code is active and the starter is engaged (key in pos 3)! As a safety critical device, it has a double contact and an addtl. plastic housing to prevent from dust. AFAIK, it is specified to work properly for 10 years lifetime even without a single actuation. However, as even the newest 6ers are now older than this, some troubles may arise....


OBC Display Bulb Replacement - Don (dis933@hotmail.com)

Here is the combined wisdom of several 6 owners on how to replace the OBC display back lighting. I do not know who wrote the second section, but it was forwarded to me by Al Stensby alnmo@pacbell.net, who stated that he saves all the good tidbits. I wrote the first section, based on my own experience. Note that I also replaced the AC fans and the OBC pushbutton lights.

Note that the first section covers 1987-1989 635CsiA models.
The second section covers precious models.

Section 1
1. Remove the right and left under dash covers. Drop the glove box by removing the pins from the hanger brackets. Note that the left one has about 10 screws, 5 for the panel and 5 for the knee bolster. One of the panel screws is by the heating duct. Pull the bolster backward and it will slide off the pins.
2. Remove the center console --- if you have a '87 on 635 you need to start at the rear AC and unfasten the armrest, etc. so that it would lift up and slide about 1" back. Remove – lift out -- the cooler tray, remove 4 screws under it. Remove the side panels (1 screw ea.) and then the 2 screws per side. Now the AC top panel with vents and controls should lift and slide back about 3".
3. You then have to remove the hand brake cover -- one screw under the horse hair -- naturally you have to remove all the seat controls switches. Finally you remove the shift lever cover - pop off the right side panel on the auto shifter – the one with the switch – disconnect the 2 connectors -- then you have 3 small screws to remove to get the left section off the cover off as well as two connectors - to remover the lever handle, loosen the Allen screw on the back of the handle) and all the window controls. You have to remove 5 screws to get the console loose -- two on either side of the console (look from below) that hold it to the dash, two way up the footwell in the carpeting, and one under the shift lever cover.
4. Remove the radio
5. Slide out the console -- note that on auto tranny cars there is a white connector that is just under the console, behind the ash tray, which needs to be disconnected. It is white with 9 pins -- and the lower part is held in by a bracket. This connector is a PITA, but if you do not remove it, you cannot get the console off. The ash tray jams against it. Before you slide the console all the way, you need to disconnect the green connector to the OBC, the 2 connectors to the cigarette lighter as well as the ashtray light.
6. From here remove the OBC – 4 screws – and go to step below.

Section 2

Instruction for pre '87 models (without rear AC)


I haven't seen a repair FAQ specifically designated for the 6 series on the topic of OBC Backlight Repair/Replacement, so I decided to create one
myself. I tackled the job tonight, and found that it isn't as difficult as it is often made out to be. (At least for the six series, it is not too
complicated, just tedious) My mechanic quoted me $80 to do the job, I did it for $2.50 and all it took was a few hours! Anyways, here is my step by step
instructions on how to replace your backlight on your e24. (NOTE- These backlights DO burn out, if you've never done this or seen it done, SAVE this
message, you may need it in the future!)

Parts needed-
-OEM Backlight Replacement. (You can obtain from dealer, or parts house...it's made by VDO I think. Costs about $20 roughly)
-- OR --
- If you're handy with a soldering iron, you can buy the replacement bulbs from Radio Shack. (Which is what I did, costs about $2.50) Radio Shack parts
number 272-1140. They are six volt bulbs, 1 volt more than the old bulbs. (No problem, the circuit board can handle 19 volts max.) Buy 2 of these bulbs. You
may need one or both.

Tools needed-
-Flashlight or worklamp (if you're working in your garage or at night.)
-Phillips head screwdriver
-Philips head screwdriver with a small handle and shaft(to reach in the tiny spots)
-Needlenose pliers
-Rachet with long neck, and a 7mm socket
-Tiny, tiny flathead screwdriver to pop plastic plates. (head has to be paper thin so you don't damage the plastic!)
1. Remove the radio, this makes the job a heck of alot easier! You can pull it from the car, or leave it resting next to the gearshift, your choice.
2. First of all, you need to remove all the screws that attach the center console to the dashboard/car. If you already know how to do that, skip to step
3. If not, read on.....
a. Lower the glovebox, and remove phillips screw on the right side of the center console. (It is visible)
b. Remove screw in carpeting, just below the glovebox.
c. On the glovebox side(not under the glovebox), there is a screw where the center console meets the dash. It is tipped upside down and tucked out of sight, but if you stick your head and look up underneath, you should see it. Remove it.
d. Pop the leather shift boot off the console (it's clipped in, gently pull it) and lift up the gray insulation. (note- you don't need to tear it out, just move it out of the way.) There is a screw to the south of the gearshifter. Remove.
e. Next comes the fun part, you have to remove the plastic case underneath the steering wheel on the drivers side. (It stretches from the door to the center
console, right above the pedals, you can't miss it) All of these screws are visible, you just have to stick your head in there and look for them. (Worklight comes in handy here) There are 5 total, I believe, all phillips head. After you get all of the screws removed, it should be able to just fall to the floor. Good. Leave it there, you don't need to pull it from the car. When you're removing it, be careful not to pull any wiring or disconnect the circuit breaker switch. Now, you can remove the 2 screws on the left side, and the one in the upper corner. (Screws are in the same location as the right side.)
f. Now, you need to loosen the parking brake plastic housing. (where the electric seat controls are -- if you have them) This is where the very small flathead and rachet comes in. Take the mini flathead, and pop the 2 plastic covers off the back of the housing. These covers are visible, and are slightly off color to the rest of the plastic. Take great care in removing them, you don't want to poke any holes in the plastic. Straight down, there should be a nut in each hole. Remove the nuts, and gently slide the housing back toward rear seat. Once again, we're making room for the center console to slide forward, so we don't need to remove this from the car.(PS-Be careful when removing the nuts, they can fall down in the seat railing.)
3. With the housing clear, gently slide the console forward. All you need is enough space to get at the 2 screws on top. So, maybe 5-7 inches. No need to yank it out.
4. Remove the 2 top screws on both sides. These screws support the black plastic centerpiece that the radio, balance control and computer are attached
to. There is also a screw directly below the black centerpiece, right above the ashtray. It's on the outside, so just feel underneath for it. Use the small headed phillips to remove this one. (Don't forget to put it back!)
5.There is also a screw behind the console, but you can't get to it. It's just a little one that sort of supports the centerpiece. You should be able to remove the centerpiece without removing the screw, because it is barely attached.
6.With the centerpiece removed, now you can finally get at the OBC! Remove the 4 phillips screws that attach it to the centerpiece.
7. The OBC will break free from the centerpiece, and on the right hand side there is a white plastic piece with a picture of a lightbulb on it. This is the backlight. Take your needlenose pliers and *gently* (what's your hurry?)pull it out. Now....
a. If you bought the backlight replacement part from your dealer or parts supplier, slide it back in where the old one was. Turn on the car to test. Reverse the removal instructions to get everything back together, and your'e done!
b. If you bought the replacement bulbs to solder in, check to see if one or both bulbs are burned out. The way the circuitry is designed, if one bulb burns out, the other does not function. If you're going to do one, might as well do the other. The circuit board is fragile, so be careful. Un-solder the old bulb(s) and solder in the new! For those with little or no experience with soldering –The solder points should be cleanly soldered. Make sure there is no solder run off un to the other connections, this will cause a short and the backlights will not function. Reattach, and reinsert into OBC. Reverse the removal instructions to get everything back together, and you're through!
a. Replace the OBC buttons light – this one is one back of the unit and is recessed. You need to purchase this bulb assembly from the dealer or similar. It is a bulb in a plastic holder.
b. PS: if you ever need to replace just this bulb, see the instructions on how to do in an other FAQ.
Once I had the parts, it took roughly 2 hours to complete (4 hrs on a '89 635!). An 80 dollar job for $2.50! FYI-There are NO shortcuts for this job, so don't even attempt to cut corners and try to bend things around. You'll get frustrated and damage your car. You gotta do it this way, unless someone has invented a better way that I don't know about! Anyhow, if anyone has any suggestions or modifications to this, go right ahead! I don't claim to know everything! Good luck!


OBC Touch Pad Bulb Replacement - "Don S." <DIS933@hotmail.com>

Get a replacement bulb for the OBC from the BMW dealer -- this is a bulb mounted into a plastic holder, that has 2 connecting tabs, and a square plastic rear end. That square tail end is about 1/4" per side and about 1/2" in length. The same bulbs are used for the illumination of the dashboard gauges in most cases. Note that some of these bulbs have a hexagonal tail end -- you do not want this variety.

1. Open the glove compartment tray!! Unfasten the two holding straps.
2. Remove the 2 screws (on '87-'89 models) that hold the black cover over the glove compartment. Drop the cover into the tray -- you may want to disconnect the wires from the light.
3. Stick you hand into the opening between the dashboard and the leather (?) panel -- just behind the OBC. Try to feel for a hole in the OBC of about 1/2 inch, right in the center of the OBC. In this hole the light bulb resides!!
4. Now for the tricky part --- get yourself a stiff piece of sheet metal -- no more than 0.020" thick -- and about 1"x2" in size. Bend the piece (the 1" side) into a square tube of 2" length -- where each side fits the tail end of the bulb. The entire "tube" has to fit snugly over the bulb tail and NOT extend past the flat of the bulb plastic holder.
5. Take this formed tube and insert it into the hole of the OBC by reaching behind it. Twist the tube to unseat the bulb and remove tube. Feel the end to validate that the bulb was removed and is in the tube.
6. Insert the new bulb into the tube -- the same way as the one you removed came out.
7. Insert bulb into the OBC hole and twist to seat -- remove tube. Validate that the bulb has remained in the socket.
8. Turn your lights on and observe -- if you got it right the buttons will illuminate!!!!
9. Reinstall the glove box tray, etc.
10. Congratulations -- you just saved yourself about 3 hours of work required to get to the OBC, if you had removed the center console.

Interior Light Timer Control Module Repair - Bill Wolf (billwolf@ixpres.com)

Description: The Interior Light Timer Control module contains an electronic circuit that controls the on and off operation of the interior light as well as a fixed timed-off delay. Although the circuit can malfunction because of a failure of numerous components, an electrolytic capacitor used in the delay function has a much higher failure rate than the other components, is known as a component type to often degrade with age, and its failure is fairly easy to identify. A new Interior Light Timer Control module costs between sixty and ninety dollars while the cost of the component is only about fifty cents, so the replacement of the capacitor may be substantially more cost effective than replacement of entire module.

In brief, if you have this problem, are handy, and want to save a few dollars, you may want to consider replacing this circuit component and repairing the module yourself.

Applicability: Suspected 1982 through 1989 (1982 unconfirmed).

Normal Operation: The circuit is designed to initiate a delay only when the driver's exterior door handle is lifted while a door is opened, so there should be no delay in entry through the passenger's door or in exit through either door. Also, turning the ignition switch to the run position cancels the delay. Proper operation of the module also requires proper signals form the driver's door handle switch, both door switches, and the ignition switch as well as battery voltage and a ground connection.

Faulty Capacitor Symptoms: Erratic operation, no delay time, short or inconsistent delay times, and flickered before going off.

Module Location: The Light Timer Control module is located adjacent to the Accessory Connector and the Chime Module on the left side of the driver's foot well (confirmed 1985 through 1989).

Replacement Component: The capacitor is a common 100 uF, radial-lead, 16-volt or higher electrolytic capacitor that is readily available at any electronics store including Radio Shack. The existing value should provide a delay of approximately 10 seconds, thought this is not a precisely-timed delay. Should you want to increase the delay, simply select a proportionally-larger capacitor, though be aware of the physical-size limits. As long as the voltage rating is marginally higher than the maximum working voltage (which may be as high as 14.4 volts on an automobile), voltage is not critical, thought capacitors with higher voltage ratings are generally larger (and more expensive), so don't get one physically too large for the allotted space on the PC board. And, radial leads extend from the same end as opposed to axial leads which extend from opposite ends.

Repair Procedure: Simply remove the module from the socket, unbend the tabs on the bottom, and remove the circuit board from the case. Next identify the capacitor. It will, in all probability, be cylindrical in shape and probably be marked with its component value and rated voltage. The capacitor location was marked by C2 printed on the PC board used in the unit I repaired, but different manufactures (if there are more than one) may possibly vary on this. The only larger component is the relay, so it should be easy to identify. Next, note the polarity marks (a plus or minus or a bar for minus) on the capacitor and any corresponding marks printed on the PC board. This is to insure that when you install the replacement, that you install it with the correct polarity. Unsolder the leads from the opposite side of the PC board using desoldering braid or equivalent, remove the old component, correctly insert the replacement component noting the polarity, resolder, and reassemble the module.

Radio (After-Market) Install - "Gene M." <mclan@worldnet.att.net>

I have seen old posts that said an aftermarket radio could not be used with BMW's separate amp in the trunk set up (86 & 87 models, and maybe 88 & 89). Those posts said that you would need to run new speaker wires from the
aftermarket unit and bypass the factory amp. From my own experience, this is not correct. You can install an aftermarket radio and run it through the BMW amp. All splices can be made on the wires going to the stock radio (summary of splices below).

I think the reason it was originally thought that this could not be done is that the stock radio only has one wire for the left channel (yellow) and one wire for the right (blue)--although the plugs themselves have two prongs. Aftermarket radio wiring harnesses have 2 wires for each channel, so how are you going to splice the speakers into the existing wires?

In my 86 635, I installed a Sony MDX C800 (depth of 6 1/2 inches). Crutchfield's sent a free adapter to plug the left and right front channels into the 2 existing speaker connections for the stock radio and everything worked fine with the existing amp and speakers. I thought the adapter was needed, but I later found out that it is not.

In my 87 635, I installed a Sony XR 2300X without using a Crutchfield adapter for the speakers. I simply spliced the postive front speaker wires from the radio to the yellow and blue speaker wires in the car's wiring harness that plug into the stock radio. The negative speaker wires from the new radio's harness remain unconnected.

One thing to keep in mind is that the current to activate the power antenna on these cars also turns on the amp. If your radio is not activating the power antenna, the amp will remain off and you get no sound. So if you have a unit like a Sony MDX C800 where running the radio in MD mode cuts power to the power antenna lead, the solution is to attach the radio's amp output line to the car's power antenna lead so that the BMW amp will turn on in all of the radio's modes.

On rear speakers, there is a quick and simple way to get 6x9 speakers in the rear enclosures. There is ample depth in the speaker well for 6x9's (I went with Polk dx9 because of their shallow mounting depth but there is room to spare)--it's just that the existing speaker grills are rectangular and you need to place the speakers under the rear deck platform to put the
OE grills back on. I placed some foam pads under the speakers and then worked the speakers down into the opening. The foam pushes them up against the bottom of the rear deck platform and they stay put and do not vibrate. I used some 3M windshield seal (it's like black sticky plumber's putty that is rolled up) around the edge of the speaker enclosure and pressed the grills back down into it. All done--appearance is completely stock and it will be very easy to change out speakers. My thanks to the group on compiling info on what 4x6 speakers will fit.

I'm not an audiophile and I'm sure aftermarket amps and heavier speaker wires would improve the sound, but the sound is clean and there is enough reserve volume to keep my kids happy. Of course you can't use the aftermarket radio's fader control (you set it for full front), but the car's existing thumbwheel fader control works fine.

One other note, the factory amp has an internal fuse. If your factory amp is not working, open it up and check the fuse.

Summary of Splices

Aftermarket Radio Wires Car's Wires
Positive front left speaker Yellow
Negative front left speaker Unconnected
Positive front right speaker Blue
Negative front right speaker Unconnected
12 volt constant power Red/Green
12 volt with key on Violet/White
Power antenna (or amp out if certain modes do not activate the power antenna White
Ground Brown
Rear speaker wires (radio fader set to full front--
car's thumbwheel fader is operable)

After-Market Radio Install (another input) "Riad S. Wahby" <rsw@jfet.org>

I just did an aftermarket radio install and I thought I'd share my experience with y'all in the hopes that it'll be useful to someone else.

First, don't listen to radio salesmen who tell you that a new head unit won't work with your factory system; they're either misinformed or trying to get you to buy more stuff.

The stock system in my 1988 M6 was set up like this: the head unit in the dash puts out two signals, the left and right channels. These go through the front/rear fader unit (mounted in the pop-out panels below the head unit next to, e.g., the heated seat switches), which is nothing more than two potentiometers. The audio signals from the head unit are carried on a yellow wire (left) and a blue wire (right); these connect to the fader unit. The fader has six other wires on it. The blue/red and blue/black wires are the right front and rear outputs, respectively. Similarly, yellow/red and yellow/black are left front and rear. The remaining two wires are both ground.

The blue/red, blue/black, yellow/red, and yellow/black wires run to the trunk, where they connect to the power amplifier (mounted aft of the power antenna and outboard of the battery). In addition, a white wire runs from the head unit to the power antenna and to the amplifier. This wire carries +12V when the system is on, telling the power antenna to extend and the power amplifier to turn on. Both the antenna and the amplifier are controlled by the same signal, which is why the antenna extends even when you're rockin' to your Huey Lewis tapes with your stock sound system. My aftermarket head unit has separate antenna and power amplifier control wires, so in my installation the antenna is only up when the tuner is in use. If you want to continue using the stock amplifier and don't want the antenna to extend when you're not using it, you'll have to run another control wire and buy a head unit with separate amp/antenna signals.

If all you want to do is change the head unit, you have two options: to use the stock fader control (if, for example, your new head unit only puts out two channels), connect the left signal to the yellow wire and the right signal to the blue wire. To use all four channels from your new head unit, connect the speaker outputs from your head unit to the blue/red (right front), blue/black (right rear), yellow/red (left front), and yellow/black (left rear) wires which were originally connected to the fader control. In the latter case, the solid yellow and solid blue wires are not used. Note that either way you do it, in this configuration the negative speaker wires are not used. I'd be wary of grounding them, since some amplifier designs might not like that much. Try leaving them floating first, and only ground them if that doesn't work; this should minimize the risk of blowing up your spiffy new head unit.

Since your new head unit likely puts out a bit higher voltage than the stock system, it's a good idea to turn the volume _all_the_way_down_ when you first test your new installation. When I did my install, I first tried to use the preamp outputs from my new head unit to drive the stock amplifier. Unfortunately, I found that even the "4 Volt" preamp outputs on my head unit did not give enough juice to get to a reasonable volume with the stock amplifier, so using the speaker level outputs is really your only option for connecting a new head unit to the stock amplifier.

While you now have a working sound system with a new head unit, the stock amplifier is pretty weak. It'll put out maybe 15 Watts per channel (at a whopping 10% THD!), so don't count on more than 8-10 Watts with any quality. As the stock speakers aren't all that sensitive, you're not going to get much sound out of your system before your amplifier starts to go south. If you're not interested in doing a complete stereo refit, you can just get rid of the stock amplifier and use the built-in amp from your head unit. The one I purchased can put out almost 20 Watts into 4 Ohms at <1% THD, a substantial improvement. In my car, the stock speakers were of the 4 Ohm persuasion, so there's no problem driving them directly from the head unit.

In order to make bypassing the stock amplifier as easy as possible, I didn't rewire all the way to the rear speakers. Instead, I used the {blue,yellow}/{red,black} wires to drive the rear speakers and only ran new wire for the front speakers. In order to do this, I unplugged the wiring harness from the stock amplifier and connected the blue wires directly to the right rear speaker wires in the same harness (in my wiring harness, the positive terminal of the right rear speaker is the white/black and the negative terminal is brown/black and located adjacent to the positive wire). The yellow wires went to the left speaker in the same fashion (purple/black and the adjacent brown/black). More specifically, the connection is now from the head unit right rear speaker outputs to what used to be the right channel wires (blue/red for positive, blue/black for negative), which go to the amplifier harness in the trunk. At the amplifier (remember, unplug the amplifier), I cut the wires off the connector and hooked blue/red to white/black and blue/black to brown/black (make sure you're connecting to the adjacent brown/black, not one of the other brown/black wires in the harness). The same goes for the left rear outputs, the yellow/{red,black} wires, and the {purple,brown}/black wires in the amplifier harness.

To get signal to the front speakers, I ran short lengths of high quality wire from the head unit to the kick panel speaker locations. Connecting the front speakers is slightly tricky, since you have to make sure you've got the crossover connections right. The back of the woofer should have three wires running to it, two on one side of the magnet and one on the other. Leave the wire on the side by itself connected just as it is. Disconnect the positive wire from the other side of the woofer (the one on the narrower spade) and connect the positive wire from the head unit to this terminal. Now connect the negative wire from the head unit to the wider spade, but make sure to _keep_the_old_negative_connection_in_place! If you don't keep the old connection, you don't get any sound out of the speaker at all. To recap: leave the lone wire connected (this goes to the tweeter), keep the negative wire connected, adding your new negative wire to the same terminal, and disconnect the old positive wire, replacing it with your own.

Routing the wires from the head unit to the kick panels is pretty trivial, except that you're going to need to remove the ECU box from above the glove compartment to get to the tunnel through the bulkhead on the passenger side. Removing the glove compartment will make the whole thing much easier. The driver's side is pretty self-explanatory.

One final comment: if you're considering replacing your speakers, check what you have before you believe what Crutchfield tells you! In my M6, I had 4x6" speakers in the front (tweeters in the door, woofer on a plate in the kick panel) and 5.25" component speakers in the rear. Crutchfield correctly reports 5.25" in the rear, but claims that I have 4" speakers in the front (it's a 4" driver, but the mounting is clearly for a 4x6"). You might want to get 4x6m ("metric") speakers (or at least make sure there are 4x6m holes on your 4x6" speakers---Infinity Reference speakers have these for sure), since the European mounting holes are slightly different from those in, e.g., GM vehicles. If it's compatible with older VWs, it's compatible with the kick panels in the M6. If you're willing to do some minor fabrication, you can get 6x9" speakers into the rear speaker pods.

See http://www.lexam.net/peter/carnut/speakers.html for details.

Hope this helps someone out.

Converting from a Four Filament Headlamp System to a Six Filament System - Scott Andrews <scott@cogenia.com>

Like many such cars, my 1980 Euro spec BMW 635 had been somewhat butchered during the Federalization process. One of the Federalization steps was to toss out the high quality European spec headlamps and replace them with cheap sealed beam units. This not only resulted in poorer lighting, but it also ruined the look of the headlamps, and included a lot of dubious wiring.

Daniel Stern (http://www.danielsternlighting.com) has compiled some useful information on overall lighting systems. Also Joseph Peterson published a very good article on rebuilding the front wire harness and replacing the crappy lamps with high quality units. (http://www.geocities.com/josephpatterson/Cibie_CSR_page_1.html?1034913276280)

The best lighting systems typically use two types of lamp. What is commonly called the H1 unit is a single filament high beam lamp. The position of the filament in the reflector, and the intensity of the lamp make for a beam that lights the road in a long far reaching beam. The other lamp is commonly known as an H4 (these are Hella names, so others may use slightly different conventions). The H4 is a dual filament lamp that has the same high beam filament, and a second low beam filament. The low beam filament is positioned differently, so it lights up the road in the relatively nearby front of the car. I also think the H4 headlamp bucket and lens tech to aim the light for the high beam down a bit, so when both high beams are on the car seems to light up the entire road, from close in front all the way out to Zion.

This solution works quite well, except it doesn’t fit well in the BMW headlamp wiring. The issue is that the BMW is made for a four filament system (A single hi/low lamp on the outer lamp position, and a high beam in the inner lamp position). Most of the articles I have read have incorrectly wired the four to six filament conversion.

When using six filaments you are seeking the following lamp behavior:

Low Beams: Outer LOW beam filaments ON, Outer HIGH beam filaments OFF, Inner HIGH beam filaments OFF

High Beams: Outer LOW beam filaments OFF, Outer HIGH beam filaments ON, Inner HIGH beam filaments ON

The idea here is to use the inner high beams to light the road directly in front of the car, and the outer high beams to light the whole world way out ahead. There are two other important things to consider when going to this setup.

1) You do not want to have the high and low beam filaments in the H4 bucket on at the same time. This generates too much heat and will cause the filaments to fail early.

2) You do not want to run the inner and outer high beam filaments off the same wires, since this will draw a lot more current through the wire and will cause both heating and voltage drop (if it doesn’t also blow a fuse).

In many of the articles I have read the wiring system fails to meet one of these two goals. In many diagrams (Stern’s for example) they use single pole single throw relays to control the lights. These do a fine job of controlling the lights, but they either leave the outer low beams on with the high beams, or they double up the current on the high beam wiring when the hghi beams are on.

To avoid this, I developed the circuit shown below.

In this circuit, I use Bosch 0 332 209 150 relays. These cost about $18 each and I had to order them since they are not your typical cheap headlamp relay. The really useful thing about them is that they are single pole double throw relays, so we can do some cool switching using them.

The operation of the circuit is as follows: In low beam mode, the left and right low beam wires are powered from the standard BMW lighting relays (in the fuse box). This current passes through the two new relays (in terminal 30 and out terminal 87a) and on to the outer low beam filaments. The relays are normally in this position (that is when the coil is not activated by passing current between terminals 86 and 85).

When the high beam switch is closed, the BMW high beam relays activate the high beam wiring. So, for a four wire system, we would have both the high beam and the low beam wires hot. The high beam wiring is connected directly to the high beam filaments in the outer H4 buckets, and also to the two new relays. So, when the high beams are on the relays switch over so that the low beam signal goes to Terminal 87b. This is routed to the inner high beam filaments. Using this setup, the high beam current is basically used to switch the low beam current from the outer low beam lamps to the inner high beam lamps. Only one filament is run by any one of the four lighting wires.

In installing this system, I placed the relays on the left inner fender right next to the battery. I also rewired the headlamp harness using heavier wires, and that allowed me to add the extra wires for the fifth and sixth filaments. So, I have the four original lighting wires coming from the fuse box down through the harness to the battery area where they emerge from the harness, and drop down to the relays. The six new wires go back up from the relays to the harness, where they head out to the front of the car, as originally designed.

Bill Wolf (from the Big Coupe Groupe) suggested the alternative wiring shown in dashed lines. This basically crosses over the right and left inner high beams so that if you blow a headlamp fuse you can still get both sides of the car lit.

In use, this system works extremely well. The effect of the low beam switching makes the lighting changeover rather dramatic, and unlike the four filament setup, the high beams in the outer position really add to the overall lighting effect.

Going to good euro lamps was a huge improvement. Wiring them properly just makes the whole thing that much better and more reliable.

Three Different Headlamp Wiring Configurations Used on US 6 Series ("Bill Wolf (Car Stuff)" <billwolfcarstuff@ixpres.com>

Basically, there are three different headlamp configurations used on US model 6 Series BMW's. The major difference is between pre-1983 and post-1982 models and corresponds to the 1983 fuse panel change, but there is also a Three Different Headlamp Wiring Configurations Used on US 6 Series

Basically, there are three different headlamp configurations used on US model 6 Series BMW's. The major difference is between pre-1983 and post-1982 models and corresponds to the 1983 fuse panel change, but there is also a difference between pre-1988 and post-1987 models that corresponds to the use of ellipsoid headlamps. These distinctions become very important when troubleshooting switch, fuse, relay, and lamp problems, and can be very confusing if you are obtaining troubleshooting help from a source having the inappropriate configuration.

Specifically, the pre-1983 US headlamp-circuit configuration was also used in the E28 5 Series and is accordingly depicted in the Bentley 5-Series Service Manual in Section 22, Figure 4-1. In contrast, it is almost completely different than the two newer configurations which are depicted in the respective ETM's for model years 1983 through 1989. It also appears that the change was made in the 1983 model at the same time the fuse panel was changed from the one containing 17 fuses to the one containing 30 fuses, but this has only been confirmed on US models. Accordingly, those with the later configurations should disregard the wiring diagram depicted in the Bentley manual and use the headlamp-circuit diagram from the appropriate ETM. It also appears that the headlamp wiring remained unchanged from 1983 through 1987, so the wiring depicted in any one of those five respective ETM's should be the same. Also, it should further be noted that although the headlamp and fuse panel changes appear to correspond to the approximate time of the mid-1982 body change, there are some anomalies in the dates that indicate the body change to have occurred in mid-1982 (3/82 or 5/82) while the headlamp and fuse panel changes were indicated in the ETK as made in 9/82.

Regarding the second change, in post-1987 models the wiring to the headlamps was again altered to accommodate the use of the ellipsoid headlamps that contain four filaments as opposed to the six filaments that are used in the standard sealed-beam or H4/H1 systems. This lighting-configuration change also affected the configuration of the relay used for high beam activation, so be make note that the high-beam relays on pre-1988 and post 1987 models are not interchangeable. (See the separate article on relays for details.)

Regarding Euro models, Ellipsoids were also introduced in 1988 Euro models as well, though there were some differences in the design. US Ellipsoid systems used 55-watt HB4 (9004) bulbs for the low beam lamps and 65-watt HB3 (9005) bulbs for the high beam lamps, while Euro Ellipsoid systems used 55-watt H1 bulbs for both the low and the high beam lamps. Regarding what was used on Euro series BMW's prior to the use of Ellipsoid headlamps, the E28 5 Series and the E23 7 Series were equipped with H4/H1 six-filament systems, but the E21 and E30 3 Series and the E24 6 Series were equipped with a four-filament system using only H1 bulbs.

As a check for the pre-1983 and post-1982 configurations you can differentiate between the older configuration and the newer configuration by using the high-beam indicator. On the older configuration the indicator is connected to the high-beam switch so the indicator will operate with the headlamp fuses and relays removed. On the newer configuration the indicator is connected to the right high-beam lamp so the indicator will not operate with the corresponding headlamp fuse removed and/or the high-beam relay removed. Also, the newer configuration has cross-wired high-beam lamps (in the non-ellipsoid models) so that if one fuse is disabled you lose one high-beam on each side instead of two on the same side (which, by the way, may be an easier test).

Electrical Relay Information and Replacement Guide (1983 through 1989 Models) "Bill Wolf (Car Stuff)" <billwolfcarstuff@ixpres.com>

The 1983 through 1989 6 Series uses over twenty electrical relays of various types. Some are specialized devices, some are located within other devices, but about half are standard, automotive-type, replaceable, plug-in units that have replacements provided by numerous suppliers including Bosch, Hella, Siemens, and Wehrle. Attempts at replacing these relays using BMW part numbers has typically resulted in at least some confusion from changes and superceded part numbers, having to use overpriced dealer parts, and the possibility of acquiring an occasional incorrect part configuration and possibly a less-than-ideal replacement. As it turns out, however, there are only three or four different relays required for all of these standard relays and the cost of each is typically between five and ten dollars depending on the brand and supplier. For those not interested in all of the details there is a summary listing at the end.


Nine of these standard relays are mounted inside the fuse and relay panel. These are designated K1 through K9 and include relays for the auxiliary fan at normal speed, the horn, the high-beam headlamps, the low-beam headlamps, start-mode unloading, the auxiliary fan at high speed, additional start-mode unloading, the fog lights, and the power windows respectively. Depending on the model and year of the vehicle an additional two or three of these standard relays are also mounted to the outside of the fuse and relay panel. These include the Main Relay, the Fuel Pump Relay, the fuel system Purge Relay, and the Oxygen Sensor Heater Relay. Another one or two of the standard relays are also located inside the passenger compartment. These include the Blower Select relay for the heating and air conditioning system and the Start Relay used on automatic transmission models. All of these relays are four-terminal (or 4-pin) SPST relays except the Main Relay, the High-Beam Headlamp Relay, the Blower Select Relay, and the Low-Beam Headlamp Relay that is used in 1988 and 1989 models only.

Standard Relay Types and Designations

Relays are basically switches that are actuated by an electrical coil. And, like switches, they are designated by a typically four-letter acronym that describes the switching contact configuration. The key (and often confusing) words in the designation are the terms "pole" and "throw" which are abbreviated "P" and "T" respectively. The throw designation refers to the number of contact positions not counting the off position (though the off position can be designated separately), and the pole designation refers to the number of contacts at each position. The standard designation is to list the number of poles followed by a "P" and then the number of throws followed by a "T" where the numbers 1 and 2 are typically replaced by the terms "single" or "S" for 1 and by the terms "double" or "D" for 2. Common types are therefore designated SPST, SPDT, DPST, and DPDT. And accordingly, if each switch contact is connected to one connection terminal, then the number of connection terminals or pins required for each respective SPST, SPDT, DPST, and DPDT switch would be two, three, four, and six pins respectively.

Regarding relays, the same basic principles and designations hold true for relays as well. However, by comparison, relays require two additional terminals or pins for the actuating coil so that the number of terminals or contact pins required for each relay typically are four, five, six, and eight respectively. In fact, SPST and SPDT relays are so popular in automotive use that they are often designated as just "4-pin" and "5-pin" relays respectively. However, and adding to the complication of understanding all of this, the connection terminals are not always connected exclusively one-to-one to the switching contacts but can be combined or duplicated thus making the number of connecting terminals more or less than the number of contacts. Thus, a normally 6-pin DPST configuration can become a 5-pin DPST and a normally 4-pin SPST can become a 5-pin SPST. Fortunately, this practice is not carried to extreme, but a few configurations are fairly common. Therefore, a 4-pin relay is almost always an SPST relay, but a 5-pin relay can be (a) an SPST relay with an added or duplicated connector pin, (b) a conventional SPDT relay, or (c) a DPST relay with an combined or shared connector pin. And accordingly, it is extremely important to properly select the appropriate type of 5-pin relay.

Normally Open and Normally Closed

With respect to switches, conventional switches normally remain in the position in which they were set. And, although switches can also be designed to not remain in the set position, these normally receive a special designation and are known as "momentary" switches. Momentary switches are spring loaded and return to their normal position when released. With respect to relays, because conventional relays are typically designed to remain in a set position only while the coil is actuated, they are therefore more comparable in action to momentary switches. Furthermore, to designate this action it has become customary to simply designate the un-actuated position as the "normal" position. Accordingly, a related set of contacts can be either designated as "normally open" or "normally closed," often abbreviated "NO'" and "NC." And, an SPDT relay would therefore have one set of normally-open and one set of normally-closed contacts. In comparison, SPST relays typically have normally-open contacts, although SPST relays can be designed to be normally closed as well. Such a relay, however, would normally be designated as SPST NC. Such a design, however, is typically not overly popular because it is directly replaceable by a 5-pin SPDT relay by simply not using the normally-open contacts.

Terminal (or Pin) Designations

Regarding these standard automotive relays, although there are some standard physical configurations and dimensions for the terminals, the electrical-terminal configurations are not completely uniform and not totally foolproof. So, although different relays may insert into the same socket, the electrical connections may not be correctly configured and could result in a short circuit or damaged devices. For example, although four-pin relays use four of the five terminal positions and may also insert into a five-pin socket, the coil and contact connections may not correspond. Accordingly, to identify the relay configuration the terminals are designated and typically marked with a set of standard numbers. The number "30" is used to designate the movable or common contact. The normally-open contact (that closes on actuation) is designated by the number "87" while the normally-closed contact (that opens on actuation) is designated by the designation "87a." Also, the designation "87b" is used for the second normally-open contact of a 5-pin DPST relay, and the number "87" designation is duplicated for the duplicate pin of a 5-pin SPST relay. So, in this respect the terminal designation on the bottom of a 5-pin relay should be sufficient to always fully identify the correct relay type. In addition, manufactures may also provide an imprint of the configuration on the case of the relay as well. The coil terminals are designated by the numbers "85" and "86."

Coil Configurations

The conventional method of actuating a mechanically relay is by using a coil of wire wound around a magnetic material. Current through the coil creates a magnetic field in this material which creates the force required to close the contacts. This electrical configuration of a wire wound around a magnetic material also provides the coil with a property called inductance. Inductance causes a resistance in instantaneous changes in current and will provide induced voltages to maintain a steady current when the actuation voltage is removed. These induced voltages can also become sufficiently high to arc switch and relay contacts or destroy solid-state devices in the relay control circuit. As a result relay manufacturers often provide one or more of several protective measures into a design that is specific to an application.

Typically, the most standard protective measure is simply a shunt resistor or diode installed in parallel with the relay coil. Both the resistor and the diode have advantages and disadvantages. A diode does a better job by limiting the induced voltage to less than one volt, but is susceptible to being destroyed by an accidental reversing of the polarity of the voltage applied to the coil. This diode is typically called a suppression or clamping diode while the resistor is typically called simply a shunt resistor. A second diode can also be added in series with the coil connection to protect the first diode, but this adds to the production cost and reduces the overall reliability slightly. In contrast, a resistor is not susceptible to reverse polarity, but resistor values that provide greater suppression use more continuous power and therefore produce more heat. The coil terminal that is designated by the number "86" should be positive and the coil terminal that is designated by the number "85" should be negative or ground in a negative-ground automobile system to provide the correct polarity if required.

Two Common Incompatible Configurations

With respect to the standard 4-pin and 5-pin relays there are two common but electrically incompatible configurations. In brief, the standard physical terminal configuration provides four terminals arranged in a square pattern with the fifth, if used, located in the center. To provide keying three of the outer terminals are mounted parallel to the respective sides and the fourth is mounted perpendicular. The center terminal, when used, is mounted perpendicular to the perpendicularly-mounted terminal. If the relay is oriented so that the perpendicularly-mounted terminal is located at the bottom, the upper terminal is terminal 87 and the terminal on the right is terminal 85. The bottom and left terminals, however, may be either 30 or 86 depending on the part number of the relay. Accordingly, the center terminal may be either terminal 87a, 87b, or a duplicate 87. And, although inserting a relay with the incorrect center terminal may cause a short circuit, most relays depict the relay configuration on the case to help prevent this. However, inserting a relay with transposed terminals 30 and 86 may not be as obvious. An example of this is the incompatibility between the Main Relay (depicted as a 5-pin SPST relay) and the Low Beam Headlamp Relay that is used on the 1988 and 1989 models of the Six Series (depicted as a 5-pin DPST relay), and which otherwise would be interchangeable.


Though the relay industry may have a designation for the case size, there appears to be some variation between the outside case dimensions depending on the manufacturer and the case material, typically aluminum or plastic. I found aluminum cases to be 25 by 25 by 25 mm (side by side by height) for what appear to be older Siemens relays, 25 by 25 by 23 mm for the older Hella relays, and 25 by 25 by 22 mm for the newer Bosch relays. All will fit under the rubber boots used to cover the relays mounted on the side of the fuse and relay panel. The plastic cases are typically are 28 by 28 by 25 mm but contain various sorts of mounting pegs which increase their over case dimensions.

Main Relay

The Main Relay is consistently depicted in all of the ETM's from 1983 through 1989 as a 5-pin SPST relay with two terminals designated 87. For 1983 through 1987 the relay coil is depicted with a series diode and no shunt, which doesn't make complete sense. For 1988 and 1989 the relay coil is depicted with a shunt resistor only. Because the coil is actuated by the ignition switch, voltage suppression is not critical, but still somewhat preferable. There are two Bosch replacements for this relay: part number 0 332 014 112 and part number 0 332 014 135. The first has a series diode but no suppression diode while the second has both a series diode and a suppression diode. At the time of this writing I priced them at $7.66 and $8.24 respectively. Both have the 25-mm by 25-mm aluminum case that will fit inside of the original rubber boot. Technically, the second relay is preferable. It is also possible to substitute a 5-pin DPST, but I didn't find one in the required the 25-mm by 25-mm aluminum case with the correct terminal configuration.

Fuel Pump Relay

The Fuel Pump Relay is consistently depicted in all of the ETM's from 1983 through 1989 as a 4-pin SPST relay. The relay coil is depicted with a shunt resistor. And, because the coil is actuated by the ECU, which is a solid-state device, voltage suppression is likely critical. And, like the Main Relay, which is also mounted to the outside of the fuse and relay panel, it is also covered by a rubber boot and is therefore required to have the 25-mm by 25-mm aluminum case. In 1987 for the M6 and in 1988 and 1989 the Oxygen Sensor Heater Relay was eliminated and the heater control was added to the Fuel Pump Relay, and in instances the combined relay became designated as the Fuel Pump and Oxygen Sensor Relay. For replacement part numbers see the section on 4-pin relays.

Oxygen Sensor Heater Relay

The Oxygen Sensor Heater Relay was only used from 1985 through 1987. As noted above, in 1987 for the M6 and in 1988 and 1989 the Oxygen Sensor Heater Relay was eliminated and the heater control was added to the Fuel Pump Relay. It is consistently depicted in the respective 1985 through 1987 ETM's as a 4-pin SPST relay. The relay coil is also depicted with a shunt diode. And, because the coil is actuated by the ECU, which is a solid-state device, voltage suppression is likely critical. Also, like the Main Relay and Fuel Pump Relay, which are also mounted to the outside of the fuse and relay panel, it is also covered by a rubber boot and is therefore required to have the 25-mm by 25-mm aluminum case. For replacement part numbers see the section on 4-pin relays.

Purge Valve Relay

The Purge Valve was designed to be electrically controlled by the ECU using a dedicated relay only in 1983 and 1984 on the 633CSi and on the M6, so only these models have Purge Valve Relays. 1985 through 1987 models contain a pneumatic Purge Valve controlled by a Purge Valve Temperature Switch mounted adjacent to the other temperature sensors in the thermostat housing. On 1988 and 1989 models the electric purge valve is powered through the Main Relay, but is controlled directly by the ECU. The Purge Valve Relay is consistently depicted in the respective ETM's as a 4-pin SPST relay. Except for 1983, the relay coil is depicted with a shunt resistor only. The exception in 1983 is likely an oversight in the pictorial as the omission of a shunt resistor appears in all of the remaining relays. As above, because the coil is actuated by the ECU, which is a solid-state device, voltage suppression is likely critical. Also, like the other three relays that are mounted to the outside of the fuse and relay panel, it is also covered by a rubber boot and is therefore required to have the 25-mm by 25-mm aluminum case. For replacement part numbers see the section on 4-pin relays.

High-Beam Headlamp Relay (K3)

The High-Beam Headlamp Relay is consistently depicted in all of the ETM's from 1983 through 1989 as a 5-pin SPDT relay thereby having one terminal designated 87 and another one designated 87a. The relay coil is depicted with a shunt resistor only. Because the coil is actuated by the Combination Light Switch, voltage suppression is not critical, but still somewhat preferable. I found one Bosch replacement for this relay: part number 0 332 204 401. This relay has a resistor shunt to provide voltage suppression. At the time of this writing I priced it at $5.59. It also has the 25-mm by 25-mm aluminum case described above, though a relay with the 28-mm by 28-mm plastic case would also fit as well.

Low-Beam Headlamp Relay (K4)

The Low-Beam Headlamp Relay was changed from a 4-pin SPST to what is depicted in the ETM as a 5-pin DPST in 1988 models to accommodate the change to ellipsoid headlamps (that use four filaments instead of six and thereby retain low-beam operation with the use of the high beams). To avoid confusion note that the later-used 5-pin DPST relay (with a pin 87b) is not the same as the 5-pin SPDT relay (with a pin 87a) that is used for the High-Beam Headlamp Relay, K3.

Both the earlier-used, 4-pin SPST and the later-used, 5-pin DPST K4 relays are depicted with a shunt resistor only. And, because both relay coils are actuated identically by the Combination Light Switch, voltage suppression is not critical, but still somewhat preferable. Also, because the later circuit configuration will accommodate either a 5-pin SPST relay (with a second terminal 87, as originally equipped, and as depicted in the ETM's) or a 5-pin DPST relay (with a terminal 87b), either configuration will work equally well. However, also note that although the 5-pin DPST relay may be replaced by a 5-pin SPST relay, it may not be replaced by the relay used for the Main Relay, because the pin configuration of pins 30 and 86 is not the same. For 1983 through 1987 vehicles see the section on 4-pin relays for replacement part numbers. On 1988 and 1989 vehicles the original relay is marked with BMW part number 1373912.3. This part number (assumed to be 61 31 1 373 912 in eleven digit form) is no longer current. I have not been able to locate a replacement?

Fog Light Relay (K8)

The Fog Light Relay is consistently depicted in all of the ETM's from 1983 through 1989 as a 4-pin SPST relay. The relay coil, however, is depicted with both a shunt resistor and a series diode, although neither is absolutely required by the existing electrical configuration. Because the coil is actuated by the Fog Light Switch and the Light Switch, voltage suppression is not critical, but still somewhat preferable. The series diode, however, is definitely not required and appears to have been a likely carryover error from the previous configuration that used a different light-switch configuration. In brief, 1977 through 1980 Six Series models had a configuration-required diode installed in the wiring to the low-beam headlamp circuit. In 1981 and 1982 models this diode was removed from the wiring and was replaced by diodes in both the low-beam and fog-lamp relays. In 1983 models, however, the circuit was completely revised and no longer required the diodes. For replacement part numbers see the section on 4-pin relays.

Blower Select Relay

The Blower Select Relay is located in the right side of the center console behind the OBC. It is consistently depicted in all of the ETM's from 1983 through 1989 as a 5-pin SPDT relay thereby having one terminal designated 87 and one designated 87a. The relay coil is depicted without any voltage suppression. Because the coil is actuated by the A/C Selector Switch, voltage suppression is not critical, but still somewhat preferable. This relay can be replaced by the same relay that is used for the High-Beam Headlamp Relay, Bosch part number 0 332 204 401. This relay has a resistor shunt to provide voltage suppression. At the time of this writing I priced it at $5.59.

Start Relay

The Start Relay is only used on models having an automatic transmission. The relay is located on top of the Accessory Connector which is located in the upper left of the driver's-side footwell. For replacement part numbers see the section on 4-pin relays.

ABS Hydraulic Unit Relays

The ABS system is used on all 1985 through 1989 models. The ABS Hydraulic Unit contains two relays that are indicated by the respective ETM's to be replaceable relays. The Valve Relay is depicted as a 5-pin SPDT relay. Its relay coil is depicted with a shunt resistor. The Pump Relay is depicted to be a 4-pin SPST relay. Its relay coil is depicted without any voltage suppression, which could be a possible error. And, because both coils are actuated by the ABS Electronic Control Unit, which is a solid-state device, voltage suppression is likely critical. The cover to the ABS Hydraulic Unit is easily removable with a single screw. The Valve Relay I found installed in my 1985 635CSi is a Bosch 0 332 204 153, a gray plastic-cased relay containing a diagram depicting no voltage suppression. This conflicts with the depiction in the applicable ETM's, so it remains a questionable issue. In any event, the Valve Relay should be totally replaceable by a Bosch 0 332 204 401, the same relay used for the High-Beam Headlamp Relay and the Blower Select Relay. In contrast, the Pump Relay is physically a larger unit having a 45 by 35 by 36 mm case and having two larger-than-standard terminals. The case contains a diagram depicting no voltage suppression, which is in agreement with depiction in the ETM. The Pump Relay I found installed in my vehicle is a Bosch 0 265 003 002. These relays are accordingly not specified in the summary

Hydraulic Height Level Control System Relay

The Self Leveling Suspension System is used on some 1987 through 1989 models. The Hydraulic Height Level Control System contains a single relay that is indicated by the respective ETM's to be a standard replaceable relay. The Hydraulic Pump Relay is depicted to be a 4-pin SPST relay. The relay coil is depicted with a shunt diode without a series diode. And, because the coil is actuated by the Level Control Unit, which is a solid-state device, voltage suppression is likely critical. Though I have not viewed this relay, it may possibly be identical to the Pump Relay located that is in the ABS Hydraulic Unit (Bosch 0 265 003 002) or may be simply replaceable by any 4-pin SPST relay that both physical fits and that has voltage suppression. For possible replacement part numbers see the section on 4-pin relays. This relay is accordingly not specified in the summary.

4-Pin SPST Relays

The twelve 4-pin SPST relays (K1, K2, K5, K6, K7, K8, K9, the Start Relay, the Fuel Pump Relay, the Purge Relay, the Oxygen Sensor Relay, and the Low-Beam Headlamp Relay (K4) for 1983 through 1987) can all use the same replacement relay. There are numerous Bosch part numbers that are indicated to be replacements, but part number 0 332 014 406 appears to be the best overall replacement. This relay contains a resistor shunt for voltage suppression and has the 25-mm by 25-mm aluminum case that will fit inside of the original rubber boots on those relays that require it. At the time of this writing I priced it at $6.82. It also appears that two other Bosch relays can be used for relays K1, K2, K5, K6, K7, K8, and K9, and for K4 from model years 1983 through 1987. Part number 0 332 019 456 is orange and part number 0 332 014 454 is black. These relays contain a resistor shunt for voltage suppression and have a 28-mm by 28-mm plastic case with protruding mounting pegs, so they will not fit inside of the original rubber boots on those relays that require it. At the time of this writing I priced part number 0 332 019 456 at $6.70. Part number 0 332 014 454 was not available and appeared to show replacement by another unidentified Bosch part that may have been part number 0 332 014 406 (the aluminum-cased part above).

General Purpose Relays

Although any of the above relays could be used for various projects that require a relay, there are some that have a mounting bracket built into the plastic case which can make mounting very easy. The Bosch part number for a readily-available 5-pin SPST relay is 0 332 019 150. This number recently superceded 0 332 014 150. However, an even more versatile relay is the Bosch 5-pin SPDT relay part number 0 332 209 150. Similarly, this number recently superceded 0 332 204 150. At the time of this writing I priced them at $4.74 and $7.04 respectively. These relays do not indicate voltage suppression, so if actuated by solid-state devices, voltage suppression may be require externally if not already provided by the solid-state driver. Also, the terminal configuration of pins 30 and 86 of these relays is transposed form that of all but the Main Relay, so they will not be a compatible replacement for the other relays as plug-in replacements.

Summary Relay Replacement Listing

Main Relay: Bosch 0 332 014 135 (preferred), 0 332 014 112 (alternate).

High-Beam Headlamp, Blower Select: Bosch 0 3320 332 204 401.

Low-Beam Headlamp (K4) (88-89): ????????

Fuel Pump, Oxygen Sensor Heater, Purge Valve: Bosch 0 332 014 406*

K1, K2, K4 (83-87), K5, K6, K7, K8, K9, and Start: Bosch 0 332 014 406*, 0 332 019 456 (orange), or 0 332 014 454 (black)

ABS Hydraulic Unit Relays and Hydraulic Height Level Control System Relay: See text.

General Purpose 5-Pin SPDT: Bosch 0 332 209 150

* 25 x 25 mm aluminum case that will fit under rubber boot

General Headlamp Information "Bill Wolf (Car Stuff)" <billwolfcarstuff@ixpres.com>


Headlamps use to be either round or rectangular and a system was either a pair or a set of four. In the US headlamps were required to be sealed-beam type bulbs which meant that they were constructed with the filament, reflector, and lens as an integrated and sealed unit. In Europe regulations were different and so headlamps were designed with the reflector and lens as an integrated unit, but with the filament in a separate, replaceable bulb. There are advantages to each system, though it has generally been accepted that the European style lamps are superior at lighting the roadway.

Regarding the conventional 5.75-inch, round headlamps that fit most pre-1988 US BMW's, they consist of a set of four lamps made up of two identical pairs. One pair consists of lamps with high-beam filaments only (called H5001 in a sealed beam and H1 in the component or European style), and the second pair consists of lamps with both high- and low-beam filaments (called H5006 and H4 respectively). In 1988 and 1989 model years BMW began to equip US cars with a unique set of lamps called Ellipsoids. Ellipsoids were also introduced in 1988 Euro models as well, though there were some differences in the design. US Ellipsoid systems used 55-watt HB4 (9004) bulbs for the low beam lamps and 65-watt HB3 (9005) bulbs for the high beam lamps, while Euro Ellipsoid systems used 55-watt H1 bulbs for both the low and the high beam lamps. Also regarding Euro BMW models, prior to the use of Ellipsoid headlamps, the E28 5 Series and the E23 7 Series were equipped with six-filament H4/H1 systems, but the E21 and E30 3 Series and the E24 6 Series were equipped with a four-filament system using only H1 bulbs.

Sealed-beam lamps now have halogen bulbs, which are a separate sealed bulb within the sealed lens, are available in only one wattage level, and are considered an improvement over the old standard tungsten or non-halogen bulbs that preceded them. H1 and H4 bulbs are available in a range of wattages from 55 to 130 watts per filament and recently are available in tinted shades of blue and in specially coated glass to provide a higher color temperature. Although a selection of H1- and H4-type bulbs (called the 9000 series) are US approved and have been used in almost all newer cars, H1 and H4 bulbs and their respective lenses are not approved for highway use in the 5.75-inch lenses that fit our 6's. However, because they are considered superior in performance, many users install and use them anyway.

Recent Trends

As fuel economy became a greater concern manufacturers of US automobiles began integrating headlamp designs into the shape of the body to reduce drag and thereby increase fuel economy. The use of these headlamps pretty much precluded the use of any kind of standard sealed beam and thereby brought about legislation that allowed the use of separate bulbs. Most of these headlamps use either H1 and/or H4 bulbs or other bulbs that are similar. In many cases the designers of these new headlamps have improved the beam patterns of the newer headlamps to provide a better cutoff thus providing more light on the road ahead with equal or less in the eyes of drivers of oncoming traffic. More recently, a more efficient method to produce light is also being used in high-end automobiles called high-intensity discharge (HID). The arc producing the this light can be made smaller and can be more precisely positioned thus improving the cutoff even more than the newer bulbs with filament light sources. The color temperature of this type of light, however, is higher and causes the beam to appear more blue than halogen or standard tungsten filaments. Accordingly, they are not beyond controversy for several reasons including inferior performance in fog and the production of glare. Some oncoming drivers report that HID lamps are a visual annoyance.

As with anything that is new, improved, and costly, this new look in lighting has prompted the manufacturing of H-series and 9000-series bulbs that are tinted to provide that blue appearance. A year or so ago I read some tests results of these tinted bulbs and in general they were found to be inferior in light level per watt. Because the bulbs discard light on the red side of the spectrum by the use of a filter in order to appear more blue, bulbs of similar wattage provide significantly less light despite whatever claims might be made. But, because they are available in higher wattages, they can be capable of providing at least as much light and the novelty of the blue tint.

European E-Code H1 and H4

H1- and H4-type lenses are manufactured by Hella, Cibie, and several other manufactures including Eagle and Duromex. From what I have read and heard over the years, Cibie is considered the best, followed by Hella, which is less expensive and more widely available. The others I have heard described several times as junk, but I don't know to what degree this may be true (or not be true). And though the term junk may be very relative or subjective, these lenses may only marginally, if at all, provide the gains that are often described in switching to the H1 and H4 lamps and lenses. Importantly, the gains are not simply provided by the use of the H1 and H4 bulbs themselves, but are also a property of the design and fabrication of the lens and the reflector. The lamps are typically available with either convex or flat lenses and the high/low-beam H4 lamp is typically available with or without the internal (typically 4-watt) parking light known in plural form as "city lights".


Regarding ellipsoids, the term ellipsoid refers to a three-dimensional geometric figure whose cross sections are all ellipses or circles. A complete ellipsoid would appear to be similar to a sphere, but stretched uniformly in one or more directions. The reference in a lamp refers to the shape of a reflector which for a spotlight is normally a paraboloid. In automobile headlamps it appears to be a term that was used to describe a design that included some variation of an ellipsoid in the reflector. The term has been associated with some German automobiles including BMW from 1988 and has been associated with other features such as two-piece lens assemblies, a larger-than-usual filament mask, angel eyes, and HID lighting. It is known for claims of providing a sharper cut off and thus a longer pattern projected on the road. I have also heard of 3-Series owners complaining about them, but the complaints may have been more related to the quality of the product than with the underlying design and technology. And, if I recall correctly, BMW used them on the E30 3 Series in model years 1988 and 1989, but reverted back to conventional sealed beams in 1990 for the remaining years of the E30. I think part of the attraction to ellipsoids is that these lamps look distinctive.

Furthermore, even though the BMW ellipsoid lenses are round, I believe all the lenses are 5.25 inches (as opposed to 5.75 inches for the sealed beams and H-series lenses) and the carrier or housing is different so their mounting is not interchangeable. Because the bulbs are a single-filament type for both the inside and outside lamps (as opposed to single and dual in the sealed beams and H4 and H1 combinations), the electrical wiring configuration in the vehicle is also different. It is also interesting that H4 and H1 combinations have never been DOT approved, but that BMW gained approval for the ellipsoids. Regarding Euro versions of the ellipsoids, they are different than the US versions and can be distinguished by the fact that the rear portion of the Euro versions are fabricated to be disassembled where the US versions contain special fasteners and are fabricated to be not disassembled.

Cibie CSR Headlamps

Cibie recently developed a new lamp designated CSR for "Complex Surface Reflectors." The reports are that the improvement over E-Code H1 and H4 headlamps is comparable to the improvement of E-Code H1 and H4 headlamps over standard US sealed beams. These new lamps are claimed vastly more efficient than conventional parabolic-reflector headlamps because they use a complex-surface reflector instead of a simple parabolic reflector. The Cibie CSR 5.75-inch lamps have flat-face optic lenses. Both low and high beam units use an H1 bulb, so there are only four total headlamp filaments as opposed to the H1 and H4 combinations that use a total of six. The low-beam unit also incorporates a city light arranged such that no cutting of a headlamp bucket is necessary in order to install it. The wiring configuration of these lamps is slightly different from that of the H1 and H4 combination or the quad-sealed-beam system because the lamps are designed to be wired so that the low-beam lamps remain on when the high-beams lamps are switched on.

Replacing Standard Sealed Beams

In the 7-inch round lamps that were used on the old 2002's Osram Sylvania has recently provided two increased-performance lamps known as respectively as Cool Blue Halogen and Halogen XtraVision (claimed to be three times brighter), but has not carried this technology into the 5.75-inch round lamps. So, to replace the standard 5.75-inch round lamps with improved performance, the Euro H4 and H1 combinations, the ellipsoid units from the 1988 and 1989 models, the Cibie CSR's, and the recent HID kits are probably the four options. Regarding H4 and H1 combinations, I think it is pretty much accepted that the Cibie lenses are probably the best. The Cibie CSR's are sixty to seventy percent more in cost than Cibie H1 and H4 combinations, but there are other options including Hella lenses and HID conversions that are now down to $400 or $500, if you consider an HID conversion an improvement. Though the ellipsoids appear to have a following, they are not generally considered as good as the Cibie lenses and the cost of installation and replacement is greater. Anyone thinking about upgrading your lighting might want to continue to research the subject a little more. Daniel Stern Lighting at lighting.mbz.org (no www) is a distributor for Cibie.

Replacing Six-Filament Lamps with Four-Filament Lamps

As previously noted, Ellipsoid headlamps and Cibie CSR headlamps only use four filaments instead of the more standard six filaments. Therefore, the replacement of the standard headlamps by either Ellipsoid headlamps or Cibie CSR headlamps requires a modification to the wiring. When the Ellipsoids headlamps were introduced on the BMW models in the mid-eighties, the wiring changes were incorporated into the new fuse and relay panels which in addition to incorporating internal wiring changes also replaced the configuration of the low beam relays. So, although not impossible, incorporating these changes into the older fuse and relay panel appears to be rather involved. Accordingly, a simple add-on modification appears to be the more practical solution, at least on BMW's.

The solution simply uses one five-pin, SPDT relay for each low-beam (outside) lamp. A Bosch part number 0 332 209 150 is a good choice for the relay because it is reasonably well sealed, has a mounting tab molded into the case for easy attachment, and is inexpensive. To install the relay, simply wire terminal 30 to the low-beam lamp, terminals 86 and 87 to the existing high-beam wiring, terminal 87a to the low-beam wiring, and terminal 85 to ground. Wiring to terminals 85 and 86 need not be heavy gauge wire as the current is a fraction of an amp. In operation terminal 87a is normally closed to terminal 30 so when low-beam power is applied, power is provided to the lamp. And, when high-beam power is applied (and low-beam power is removed) the relay closes the connection from terminal 87a to terminal 30 thereby maintaining power to the lamp. And, this is all accomplished without interfering with operation of the rest of the lighting circuit.

Replacing Four-Filament Lamps with Six-Filament Lamps

If you are converting from factory Ellipsoids headlamps (which use four filaments) to standard sealed-beam or H1/H4 headlamps (which use six filaments), then the problem is somewhat the opposite of that described above. In this case the wiring to outside lamps (the ellipsoid low beams) is designed to remain on with the high beams. The six-filament lamps, however, require that power be removed to the low-beam filament and that power be applied to the high-beam filament. And, although applying power to the high-beam filament is accomplished by wiring it directly to the inside lamp, this in itself does not accomplish removing power from the low-beam filament. Furthermore, allowing both filaments in the same lamp to operate together is beyond the design capacity of the lamp and will cause excessive heat and premature failure.

Again, incorporating changes into the newer fuse and relay panel appears to be rather involved, so a simple add-on modification appears to be the more practical solution. And, again the solution simply uses one five-pin, SPDT relay for each low-beam (outside) lamp. As above, the Bosch part number 0 332 209 150 remains a good choice because it is reasonably well sealed, has a mounting tab molded into the case for easy attachment, and is inexpensive. To install the relay simply wire terminal 30 to the lamp, terminal 86 to the existing high-beam wiring, terminal 87a to the low-beam wiring, and terminal 85 to ground. Again, the wiring to terminals 85 and 86 need not be heavy gauge wire as the current is a fraction of an amp. In operation terminal 87a is normally closed to terminal 30 so when low-beam power is applied, power is provided to the low-beam filament. And, when high-beam power is applied (and low-beam power is not removed) the relay opens the connection from terminal 87 to terminal 30 thereby removing power to the low-beam filament. And, as above, this is all accomplished without interfering with operation of the rest of the lighting circuit.

Fusing Considerations

Regarding direct replacements, there are also electrical considerations. My recollection is that H5006 lamps are rated at 35/35 watts and that H5001 lamps are rated at 50 watts. The standard fuses in most BMW's are 7.5 amps, which will provide around 85 watts (or 90 watts maximum) at 12 volts (though the lamps may be rated at 12.8 volts). In a non-ellipsoid equipped US model a single 7.5 amp fuse provides power to two high-beam filaments, so there is little to spare over the 85-watt total (35 + 50) per side. Accordingly, H4 and H1 conversions can be considered direct replacements as long as you increase the sizes of the high-beam fuses. When doing this, however, it is probably not advisable to exceed 15 amps per fuse, because of the 30-amp rating on the relays that are used to provide power for two fused circuits. So, in turn, it may not be advisable to increase the combined wattage to over 170 watts per side on the high beams. With standard H4 lamps at 60/55 watts (high/low) and H1 at 55 watts, this wattage is under that and is therefore not a problem, but the higher wattage H4's and H1's may exceed this level. Regarding the low-beam lamps, low-beam power is provided through the Low Beam Check Relays so increasing the fuse size beyond 7.5 amps to provide more than 85 watts on each low beam may possibly stress or over burden these relays as this is above the original design level (though I have not heard reports of this being a problem). The existing low-beam, 7.5-amp fuses are more than adequate for the standard 60/55-watt (high/low) H4 lamps with the 55-watt filaments. Also, because the fog lamps may be wired through the low-beam relay, see also the section on fog lamps below for other possible limitations.

Electrical Wiring Considerations

Regarding adequate wire sizing, I looked up the wire size used in the headlamp circuits in my 1985 ETM and found that the low-beam circuit uses wire that is 1 square millimeter and the high-beam circuit uses wire that is 1.5 square millimeters. A table in the front of the ETM equates these wire sizes to AWG 16 and 14 respectively.

The size of electrical wiring is normally limited or rated for two types of losses: voltage drop and heat dissipation. That is why there is a minimum wire size for circuits (to allow heat dissipation) and why longer runs require an increase in size (to reduce the voltage drop). In normal 120/240-volt electrical wiring used around homes and offices AWG 16 and 14 are rated for a maximum of 10 and 15 amps respectively. This is to prevent the wires (including extension cords) from become unacceptably hot under the worse conditions of temperature, poor heat dissipation, and maximum load (including some added safety factor).

For a perspective, in a 12-volt automotive circuit 10 and 15 amps correspond to 120 and 180 watt loads, so prudence would suggested that we not fuse these wires too much over these values. Ten amp fuses should be adequate for 80 and 100 watt loads. However, the current for an H1 and H4 pair of 100 watt (each) high beams is about 17 amps combined. This is slightly above the 15-amp estimated wire rating (but not significant), and accordingly would have to be fused at the next size fuse at 20 amps. And, in this case, as you may recall, the only limitation is not just the wires, but that the headlamp relays are only rated at 30 amps. And, because one relay controls both the left and right circuits, going beyond 15 amps per circuit is actually exceeding the rated capacity of the relay. However, as a matter of practicality, exceeding the current rating by ten to twenty percent should not normally provide a problem in an overly-designed and conservatively-rated relay, but when doing so, it would be prudent to keep a spare relay on hand.

Regarding voltage drop, AWG 16 and 14 wires have about 4 ohms and 2.5 ohms respectively per 1000 feet. So, an estimated ten feet of these two wire sizes would have about 0.04 and 0.025 ohms respectively. And, at their respectively maximum rated currents (10 and 15 amps), ten feet of these wires would drop about 0.4 and 0.375 volts respectively (voltage drop equals current times resistance). Putting this into perspective, increasing to the next-larger (even number) wire size would reduce the voltage drop about 35 to 40 percent of the previous value, so the 0.4-volt loss may decrease to around 0.24 to 0.26 volts. And, that difference (0.14 to 0.16 volts) is only slightly over one percent of the full battery voltage. However, the entire voltage drop of about 0.4 volts (not just the difference) is probably less than the normal fluctuation of battery voltage as maintained by the alternator, depending on the load, charged state, and condition of the battery, so if your wiring is in otherwise good condition, you should probably have no concerns. Accordingly, it certainly would be prudent, however, if you were going to increase your lamp size, that you carefully inspect the wiring and connectors for being in top condition before doing so.

Fog Lamps

Regarding fog lamps, they are probably another whole subject in themselves. However, their wiring may in some cases have an effect on the operation of the headlamps. So, in this respect a few further comments may be in order. Accordingly, on models through 1987 power to the fog-lamp relay was provided directly from the battery, so the wattage of the bulbs used for the fog lamps does not directly affect the headlamp wiring considerations. However, on 1988 and 1989 models power to the fog-lamps relay was provided through the contacts of the low-beam relay, so the wattage of the bulbs used for the fog lamps does affect the available wattage of the low-beam lamps because the combined wattage of the low beams and the fog lamps is limited by the 30-amp rating of the low-beam relay.