The 85 Vanagon should only have one oil pressure switch (the one you already
replaced).  However this wiring system has a known problem, which is, if you
have a bare spot in your oil pressure sender wire and it touches the engine
you will get the oil light coming on.  The wire runs next to a hot engine,
and close to a hot exhaust.  If it gets too close and the insulation melts,
then you could have the bare wire touching the motor causing your light to
come on.  The reason why it comes on at different rpms is that maybe it is
flopping around in there and is only hitting the engine when the engine is
vibrating a certain frequency.  Check this wire out and replace it if it
looks beat up or toasted.  If this doesn't help then get the pressure tested
at a local garage with a oil pressure gauge.  Be sure to watch them test it
or ask for the pressure readings (in psi), as many garages will say they
tested it, but in reality they have just seen the light come on (or are just
repeating what you told them).

Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
Fax: (856)-327-2242

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