BMW E34 central locking problems and door locks
E34 central locking locks or unlocks the doors by itself, why?
The most common cause is worn, intermittently breaking wires in the harness running next to the boot lid hinge. Also check the door grommets. Other causes are worn plastic door microswitches, a seized boot lock housing or motor, and a worn key.
Why does the lock motor buzz but the door does not lock or open?
The motor may be seized or rusty when the protective rubber bellows has split and moisture has got in. The motor can be opened and cleaned, or replaced with a new one. Replacement is easy: two screws inside the door hold the motor in place. Loose mounting screws can also shift the motor.
Why does central locking not work from the driver's door lock?
The microswitches in the driver's door lock housing control all the doors, the sunroof and the fuel flap locking. They can fail when lock spray or other substances have been sprayed into the lock. The repair may require replacing the whole handle with its lock.
Where is the E34 central locking control box, and does the lock open mechanically?
The central locking relay box is under the rear seat on the driver's side. If central locking does not work, lift the driver's or passenger's door handle up and turn the key past the normal unlocking position, and the lock opens mechanically.