You were right, Ken.  The wiring was cracked and intermittently shorting
out.  I replaced it as well as the oil pressureswitch and the problem is gone.

One thing though:  While trying to diagnose it I got an afternarket
pressure switch from CarQuest.  It introduced NEW symptoms, namely the
light started going on at about 1000 rpm.  My mechanic said he never trusts
aftermarket pressure switches, so I got one from a VW
dealer.  (Interestingly, it was cheaper than the aftermarket.)  All
problems gone.  I think the CarQuest was for a higher pressure than the VW
part, but was incorrectly labeled.  I have run into this at CarQuest
before.  I replaced the rear deck struts a year or so ago with some from CQ
which were said to be for a Vanagon.  They wouldn't support the weight.  I
took them back three time before getting my money back and finally got some
VW struts from a dealer that would hold the weight.  I think CQ labels
things without knowing what they are talking about.

Thanks again for your help.

Charles
'85 Westy