mine did this a month ago.  pumped till my heart was content but no wipe,
thought is was the motor.  i checked all fuses, pump etc...  scratched my
head until i looked in bentley and found out that there is a relay that
controls the rear wiper independent of the pump.  i bought a new one from vw
for about $8.  cured it!  try that.  i think the relay was number 72 but
can't remember exactly.  it is located in fuse box right above the fuses,
about the size of pager, there are several of them if you are familiar.
chances are this might be your problem.  after i replaced that relay another
relay went out a week later, so i replaced that as well.  i guess they
pretty much start going about the same time or so.  but now all is good
good luck
jason

>From: "Chasteen, Jonathan M. MM3 (CVN69)" <chastejm@CVN69.NAVY.MIL>
>Reply-To: "Chasteen, Jonathan M. MM3 (CVN69)" <chastejm@CVN69.NAVY.MIL>
>To: vanagon@GERRY.VANAGON.COM
>Subject: rear wiper inop
>Date: Fri, 30 Jun 2006 19:00:59 -0400
>
>Not sure what to search the archives for here. My rear wiper on 85 GL
>wont wipe, it will spray all day long but wont wipe. All fuses are good
>(new I changed em all) and I tried to get the hatch panel off but
>stopped after breaking 3 of the clips. Any input?
>
>
>
>Thanks
>
>jonathan