Fixing Power Door Locks

If one of your locks stops working, never has worked or works irratically, then you can suspect one of the following:

* Loose connection, short or dirty/burnt motors.


I'm going to assume you will check all the wiring for continuity and that the motor unit is recieving a pulse of power from the control unit. To do this:

  • 1) remove door trim and cut out the protective film. Make sure your window is up.
  • 2) Disconnect the plug from the lock unit.
  • 3) Use a multi-meter set to check voltage, ground to the vehicle and test the wire one connection at a time watching the meter while you activate/deactivate the door locks. Do this while in the car.


If you see temporary jumps in the voltage you know the pulse is getting there. At this time check for clean connections on the terminals of the plug and recepticle.
If the motor is getting the power but not operating then you can suspect a dirty/burnt motor...
A burnt motor can't be fixed easy, but with luck yours is just dirty, so get ready to pull it apart - you can't break something that's already broken right?


Procedure for repairing e30 door lock assembly

Remove unit with car door unlocked - reassemble with door unlocked AND locking arm fully extended.
If your electric locks are not working, remember the door can still be mechanically locked while you take your time to work on this.
Observe how the lock components operate BEFORE dissassembly.

BMW E30 diagram of door lock mechanism BMW E30 double-lock swing arm BMW E30 door motor diagram The double lock metal swing arm.

Spring can be replaced with spring or spring(s) from computer diskettes. Put spring over pivot shaft, and one end through the little hole then put it back in and play with it positioning the spring till the arm flips back the way it should.

Opening the door lock mechanism unit:

  • 1) cut black arm sleeve lengthwise along the middle.
  • 2) remove sleeve.
  • 3) cut unit lengthwise where red and white plastic meets.
  • 4) pry apart and remove red cover carefully.
  • 5) remove locking arm.
  • 6) lift up electronic connector, motor wires attached do not force.
  • 7) remove double locking metal swing arm, has small wire spring which may snap.
  • 8) lift out the two motors, electric connector and wires together .
  • 9)Set aside white gears.

Fixing dirty motors (unsolder the wires first, note wire colours):

  • 1) check for continuity between the motor terminals and the motor brushes.
  • 2 clean brushes where they make contact with fine sandpaper till they give a shine.
  • 3) rub motor shaft where the brushes contact with a pen eraser (clean don't scratch.)
  • 4) put end back on motor and make sure the brushes are connecting to the shaft properly.
  • 5) give the motor a few good spins back and forth to seat the brushes.
  • 6) test electrical connections of motor for continuity, some resistance is normal, less is better.
  • 7) apply 12 volts to motor to test.

Notes:
- Remove the motor end carefully there are small washers which can be lost.
- Reassembly of unit: I use 2 part 5 minute epoxy, and electricians tape.


Results:

My motor now works - the double locking bolt I had to disable, it kept getting hung up and interfering with the main lock arm.
Good luck and I hope U get them fixed.

Michael S. Roberts