BMW Z3 central locking faults
Z3 central locking does not work on one door: what is the fault?
If only one door's lock does not react, the fault is often in the lock motor. Check with a multimeter whether the control voltage reaches the lock and whether the earth is fine. If the voltage is fine but the lock does not move, the motor is broken. Sometimes replacing the lock striker helps.
Z3 boot locking does not work: where is the fault?
The tailgate wiring harness can break or short under the rubber boot, so measure the wires with a multimeter. The seal of the third brake light can also leak. Moisture then oxidises the connectors and the bulbs burn out.
Z3M remote does not lock the doors although the key works: why?
The cause can be a worn switch button in the door lock that does not press fully down. The car then does not receive the locking signal from the remote command. Turning the lock's mounting piece made the door hit the switch, and the fault went away.