I had the same problem on my 88 GL. After farbling with it for quite a
while, trying to figure out what the problem was, I finally determined
that simple wear eventually gets to the locking mechanism. A loose fit
develops and then if you do anything with the van that causes any flex
in the vehicle - which is something happening all the time in normal
driving - the door pops open.When I checked with Camelback VW in
Phoenix, they told me that this had become such a problem,  VW had come
out with a fix in the form of a redesigned locking mechanism. I bought
one, and saw that indeed, the new lock was different from the old. On
installation it immediately solved my problem. This was 8 years ago, so
I can only assume the part is still available.

BTW, just a plug for Camelback - I started using them for parts some
years ago, and while they are a Dealership and therefore expect
dealership prices on most things - they have been good to work with. I
always asked for Sean (pronounced "shawn" if anyone doesn't know)  in
the Parts Department. Always let them you are a member of the Vanagon
List Group, and if you are out of Arizona, include that information as
well. You may get a bit of a price and tax break on some things.

I've got no affiliation with these guys other than being a satisfied
customer.

John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com

Marc Perdue wrote:
> Any of y'all had your sliding door not want to stay shut?  The one on
> my '87 Westy is doing just that, even when locked...  Not a fun thing,
> driving down the road and have the side door pop open . . .  What
> broken mechanical thing should I be looking for and where?  I was
> going to start with the latch on the rear edge of the door, but it's
> too cold to be working outside just now, so I'm emailing you all
> instead.
>
> Thanks,
> Marc
>
>
>