My car is a 1988, 928, S4.
Recently I had a faulty locking motor on the driver side door. I replaced the motor but found the new motor is not activating. All other electrical components for this door are working perfectly-mirror adjustment, seat memory switch all work fine. I have not reattached the speakers but that should not matter, I hope?
> Using the key to open/lock the driver side door doesn't activate the automatic locking/open mechanism for either door. While inside the car using the dashboard push button lock the passenger door cyles through lock and unlock. The drivers side door does nothing. Yes both doors are closed when activate the lock wsitch.
> Using the key on the passenger door, the lock on passenger side cyles to lock/unlock and the driver door lock does nothing. Somehow the diver side door lock is not activating.
> I checked fuses-all ok. I also checked the wiring the best I could but did not detect any non-conections or frayed wires.
> Any ideas as to the problem?
I think this may be a problem with the Control Unit Alarm System. The only problem is I have not been able to locate this control unit? Anyone know where I might find it.

 

you need to inspect the harness that plugs into the door lock motor., its possible it has pulled out.

also make sure you have attached the lock sensor wires to the harness along the top of the door its a 3 wire harness with a flat connector.

Next inspect the harness where it enters the door panel its common to have wires break in this location