Article by: Johan
Applies to: both the e32 and e34.
Problem: When locking the car with the key the deadlocking won’t engage and the total closure feature isn’t working.
You’ll find that if you use the lock on the passenger side the deadlocking and total closure features are still working.
This problem is caused by some broken pins on the microswitch which resides in the locking mechanism.
Models: This applies to all E32s and even the E34. There seem to be 2 types of micro switches.
The newer one has shorter pins. I assume this is a design improvement. The newer one I got was from an ’89 model.
Background: The central locking system is activated by a microswitch unit with 3 switches in it. For those of you who want to know it all here is a state diagram (supplied by Jon Evans) for the lock:
| State | A | B | C |
| Unlock | X | 1 | X |
| "Off" | 1 | X | X |
| Lock | 1 | X | 1 |
| Deadlock | 1 | 1 | 1 |
1 == 12v
x == floating (not connected)
If the microswitch isn’t working the door can still be locked by the mechanical rods on the lock assembly.
Fixing it: There are 2 ways of replacing the microswitch. One involves getting the entire lock assembly out. The second is more of a quick fix for the more experienced tinkerers among us.
As one can image removing the door panel might help…since most of you have done this a multitude of times I’ll just give a quick rundown 🙂
Pull off the wood trims. This will uncover two screws near the door handle. Undo these. Then start pulling at the bottom part of the panel so the clips that hold the panel come out.
Then start pulling at the top of the panel so that the clips over there also pop loose. Now you should be able to pull the door panel upwards.
Now it’s time to remove the connector that goes to the mirror switch and the courtesy lights. It might be helpful to have someone hold the panel while you undo the electrical connectors.
Now it’s time to remove the bowden cable that goes to the door handle. If you pull the cable slightly backwards it’ll pop out of the guide in the door handle. Now you can unclip it from the door handle.
Remove the two mechanical rods that go to the servo and the lock. Remove the servo as well.
To remove the lock first push the slider towards the front of the car. This will allow the door handle surround on the outside to fold off.
After taking off the door handle surround a phillips head screw and a ring around the lock cylinder are uncovered. Remove these. Now the door lock should be loose so you can take it out. There is not much room so this could take some patience.
Now it’s time to replace the micro switch. Remove the plate connecting the servo bracket to the lock cylinder.
Clip the tie wrap that holds the wire to the microswitch. Remove the Black and yellow connectors from the bracket. The bracket has two locking points on the rear side of the connectors.
Now remove the clip that holds the microswitch housing to the lock assembly.
Now you can pull out the old micro switch and install the new one. And as always replacing is reverse of removal 🙂
Before putting the door panel back on check that the servo is positioned properly. If it’s to far to one side the door can’t be opened from the inside door handle, if it’s to far to the other side the door won’t unlock.
By using the “quick fix” way. You can leave the lock in the car. First remove the covering plate (only remove 1 screw from the servo).
Then remove the tie wrap and the connectors on the microswitch wiring. Pull the clip on the microswitch housing off.
Remove the housing of the microswitch. This is kind of hard since the window guide is in the way. But it can be done !!
