> Now, buzzer goes off seemingly randomly when van is fully warmed up,
> buzzes for 10-20 seconds, stops. No knocking or anything that would indicate
> an actual oil circulation problem.
>
> Short in the sensor? I'm baffled.
>

The .9bar sensor (above 2Krpm) actually works opposite the .3bar (below
2Krpm) sensor. That is, low pressure on the .3 grounds the sensor wire, and
low pressure on the .9 UNgrounds the associated sensor wire. This means that
an intermittent connection on the .9 sensor wire can cause it to buzz, and
if the connection goes entirely it'll buzz ALL THE TIME above 2Krpm. This
happens with annoying frequency when fumblethumbs gas station greasemonkeys
do oil changes and knock the wire loose from the .9 sensor. It's worth
looking at. It's the brown wire with going to the sensor under the
waterpump, to the left of the crank pulley. It's mostly obscured by the
alt/water pump belt if you look down from the top. Pull the wire and see if
the buzzer goes solidly above 2000rpm. Then ground the wire securely and
test again. If it doesn't buzz, then the wiring and circuit board are OK--
check sensor and/or pressure.

--
John Bange
'90 Vanagon
"We'd tell a monkey how to peel a banana, if he said he was peeling one in a
Vanagon."