My '88 vanagon developed gremlins that would occasionally unlock the
locked doors. After a week of being convinced that I was the most
absentminded person on the planet - I discovered that the
central-locking system was unlocking the doors after I had locked them.

Since the central-locing system seems to be in the realm of vodoo magic
- with even Bently devoting scant time to it's workings, I thought I'd
share what I discovered so far.

Someone asked if each of the lock motors the same?

It does not appear so. Accoring to the wiring diagram, the rear gate and
sliding door motors are different from the door motors.

How I figured out where the problem was:

First:

Simply unplug the wiring to one motor - and see if the system works.
Repeat until you find the one with the problem. Pick the most likey
culpret first.

Second:

Once you have found the "bad" door, you need to figure out if the
problem is with the wiring or the motor.

Which wire does what?

Red = +12 volts power
Brown = Ground
White = Unlocked signal
Yellow = Locked signal

Make a jumper wire and connect the red wire to the white wire. Did the
other doors unlock? Now connect the red wire to the yellow wire. Did the
other locks lock?  (Note this only works for the two front doors.)

On my van, the unlocking worked fine - but not the locking.
So I think it may be a broken wire..

I'll report more as I figure the rest out.