I've had this intermittent problem with the slider door power lock on my 90
VW Westy Syncro.
When I lock either front door (from inside or from outside with key),
sometimes the slider door does not lock. Both front doors and the rear
hatch lock dependably. This is more than just and inconvenience. Sometimes
I go into a store for and hour or two and come out to find the slider
unlocked. Luckily nothing has been stolen. Yet! The problem with the slider
not locking is worse in cold weather. If I don't hear it lock when I lock
the front door I go around to the slider. Sometimes if I just pound it once
or twice with my hand from the outside I can hear the slider door lock
engage. Sometimes all the pounding in the world will not solve the problem.
If I use the key at this point to lock the slider then it won't unlock when
I unlock the front doors. (the key won't unlock it either) Then I have to
unlock the passenger door and reach inside to use the manual latch to open
the slider. However, the slider door stays in locked position so that if I
close the slider again it will be locked. This caused me to lock myself out
one very cold night when getting up to pee. It's kinda funny now, but
stumbling around in the dark on a frosty cold night, shivering with no
cloths on is not funny at the time. (Finally got in by climbing onto roof
rack and coaxing the tent zipper open.)
 :) good for a laugh but I'd like to fix it. Any ideas? (I did take off the
slider door panel and tried lubing the mechanism and the power unit)(also
tried steel wool to clean the brass electrical contact points)
Thanks for your ideas.
Bill