Help troubleshooting central locking system

[medic911]

I have a 1988 930 (cab) with central locking.

Recently the system failed. If you attempt to use the key to lock it from either the drivers or passenger side, the doors lock, then spring back open again. This tells me that the system thinks one of the doors is open.

If you close the drivers side, then open the passenger side and reach in across the seat, you can manually lock the drivers side. Then you can manually lock the passenger side and if you hold the outside door latch open, you can close the passenger door and both sides stay locked. This seems to be the only way to lock the car.

The central button on the inside console seems to function fine.

My question is:
How do I discover which door is the problem and what do i need to do to fix/adjust the culprit part? Dont really want to take both door all apart for nothing.

thx

[SpyderMike]

You can check the function at the circular connectors inside the frunk and get a clue which door is the culprit. They are located just inside the fenders where the wiring would come through the door. You can also try to access the central locking controller but it is on the right hand side up under the dash if I recall....not that easy to get to with stuff in the way.

[McLaren-TAG]

There's also a micro switch cable in there, a shockingly expensive part that I guess feeds the lock/unlock state back to the controller. I just have two available plus a controller module currently up for sale should you need them.

[ganun]

easiest thing to do is to swap the lock computer see if that fixes it ( it did on my 87)
Only thing it's kinda hidden behind the pass side trunk hinge, way back in there held with a 10 mm nut.