R&R Blower Control Transistor - 635CSi:

 

There are a number of excellent guides to this process in the b_c_g technical reference already.  As I have now had the privilege of doing this twice, I thought that some pix might help out.  We wonít go into a great deal of detail (and then again, maybe we will) and you should read the other excellent write-ups as well.  You need to know that there is no warranty on this procedure, and, of course, you do this at your own risk.  Then again, if you are a cheap ba?tard like me ,you will forge ahead.

 

The black aluminum cover is where you want to be.  Two screws

along the top back edge; four along the lower edge on the firewall.

Cut the wire-wraps off and move the wiring loom down to access

the lower screws.

See the beautiful strut-brace?  See it shine; see that its right in the

damn way!!  Be sure to drop at least one screw into the engine compartment.

 

Work the cover out and this is what you will see:

 

Yep, the blower motor and the squirrel cages.  Note that the right cover has already been removed.

 

Donít get too excited yet.  We have some other things to do first.  See the two green lines at the bottom of the compartment?  They are clipped into a holder on each side of the blower compartment.  Carefully lift them out and push them down and out of the way.

A/C Line Clips ñ one on each side

 

Next locate the two little brass clips on the upper sides of each black squirrel cage cover.

 

Thatís it on the upper right of the left blower cover.  One on each side at the top.  Pry them off and donít lose them.  Next, gently pry the latching tab on top of the blower cover downward and release the top of the cover.  Pull gently up and work the bottom of the cover free as well.  You now have to worm this cover out of the compartment ñ carefully.  Donít break anything.  Note that the cover has a slotted latch on the top and a tab on the bottom.  Remember this - thatís how it goes back - tab at the bottom and slot at the top.  Remove the round end guard and note that it has a flat spot on itís edge.  This goes back along the flat surface of the compartment bottom.

 

Now you see this:

 

 

Note the latch in the center of the blower complex.  Undo the latch and lift the blower assembly up until you can unplug the motor leads.  Theyíre sexed so you canít put them back on wrong so donít worry.  Carefully lift the assembly out and put it somewhere safe.  Nowís a good time to lube the bushings with a drop of motor oil. Donít drop this assembly, its fragile and expensive.

 

 

Ugly isnít it?  The brown and blue leads are the blower leads.  In the left intake, at the top, the object of your desire:  the blower control (just above the white towel).  That ugly blob to the extreme right is the OBC CODE horn.  Thatís what bothers the neighbors when you canít remember the code that you set.

 

Note the tab at the top of the cover.  Remember:  Slot on the top.  Tab on the bottom.  Youíll hate yourself if you get it backwards.

 

Hereís a better view.  Next problem:  remove the two bolt/nut complexes that hold it in place (right side).  Answer:  stubby flat screwdriver and a tiny wrench or pair of pliers.

The nuts are on top of the intake housing and are about 5/6/7 MM I guess.  I used my finger as they had been out once before and werenít too tight. BTW, stuff a piece of cloth or a towel into the intake to block tiny things from the depths of hell that are at the bottom end of this intake run.  Its inside the dash.  Trust me, you donít want to go there.

 

 

See the board leads?  Once you have the board free, unplug them.  They are also sexed and sized so that you canít screw them up.  Just to be safe, write the wire color down in order from front to back in case your board is different.  Now its time to go to the kitchen and get into your spouseís way.

 

Hereís the bugger that makes your life miserable.

 

The transistor you need to replace is a 2N3055.  Get a 2N3771 from an electronics supplier.  Get a small tube of heat sink grease from Radio Shack as well.

 

Look carefully at the back of the board and new transistor.  Note that the transistor leads are closer to one end than the other.  This keeps you from putting it in backwards.  Now the bad news:  the original transistor is riveted to the board.  You will need to grind the rivets off carefully and desolder the original transistor from the board.  Note that my board had a small resistor bridging the two transistor leads.  If yours has this make sure you solder it as well.  Replace the two rivets with small bolts and nuts.  Put a glob of heat sink grease on the back of the new transistor and bolt it down.  Solder the leads and resistor together.  Be careful, soldering irons get very hot and can harm you!!

 

I could injure myself with a roll of Scotch Tape!!

 

Go it done?  Back out into the heat with you.  Reconnect the board to the leads and bolt the board in place.  There isnít any easy way to hold onto the tiny nuts, but you can get you big hand in there if you try.  Hint, do the rear bolt first.

Thatís what it should look like.  You can trim the leads if you want.

 

Put the blower motor assembly back, connect the leads, and latch it down.  Now stop and make sure the squirrel cages turn freely and that the blower leads are not rubbing the cages.  Clear the tools away and try the fan from inside the car.  All should turn freely and there should be infinite speed selection from the blower control.

 

 

Now take the end guard and orient it into place.  Remember the flat spot goes towards the bottom/back flat part of the compartment.  You will have to fiddle with it to get the whole assembly back together.  Worm the top blower cover back into the space and seat it at the bottom first (tab at the bottom, slot at the top) and then the top.  Stop.  Make sure that the blower cages turn without dragging on anything.  O.K.?  Now snap the two brass clips back into place.  Repeat this process on the other side.  Test at each step to make sure the blower isnít binding on the covers.  Its hard putting the covers back on as they now hate you for disturbing them in the first place, space is tight, and the end guards keep falling out of position.  Keep fooling with it; you will get them back on eventually.

 

Once you have both covers on and clips in place, test the blower again for the inside.  Everythingís O.K.?  Good.  Snap the A/C lines (green) back into the clips carefully.  Put the black aluminum cover back on and zip tie the wiring loom back into place.

 

Think about what you have done and mentally make sure that you put it all back together the way you were supposed to.

 

Oh yeah, back the car out of the garage:

Clean kitty litter.  Sign of a happy M30.

 

Hereís that screw you dropped.

 

Thanks to Jim Booth for the info on the cross-referenced, newer, better, hopefully lasts-longer transistor.

 

Bob Duckworth