Today I was working on a very recent addition to the family van fleet, a
90 pass van, 2.1 auto towed home yesterday. It was knowingly bought with
a massive oil leak as soon as the engine was started and was presumed to
need a new engine based on assertions by the seller. Changing the oil
cooler o-ring fixed the leak. However, the oil pressure light would not
stop blinking, even if the rpm was raised.

After unplugging the 2 pin connector to the oil switches, I used an ohm
meter to determine that the low rpm switch was grounded when engine was
stopped and went to open circuit immediately when engine was started or
even cranked briefly. I verified that the oil light worked by grounding
the wire to it from the low switch with the key turned on. The light
would blink when grounded and stop blinking when the wire was unplugged.

In spite of the above all normal test results, when the 2 pin connectors
were joined, the oil light blinked constantly while the engine was
running. The blinking stopped as soon as it was unplugged again. Again
the switch itself showed open circuit while the engine was running. What
the heck?

Curious as to what was going on I unplugged the 2 pin again and bridged
the in and out ends of the low switch wire with a test jumper so I could
measure the voltage on the wire with the meter. NOW the light stops
blinking when the engine starts and resumes blinking if I stop the
engine by pulling the coil wire! WORKS normally.

In frustration I removed the jumper and plugged the 2 pin back together.
Again the light stays blinking after the engine starts! My nephew then
points out that the only difference is that it worked fine when only the
one switch was wired up by the jumper but doesn't work when both
switches are wired up as they are supposed to be. I grabbed some cutters
and clipped the wire coming from the high pressure switch. Now the oil
light works! Blinks with just key on, goes out when engine starts, comes
back on if engine is manually stalled.

Of course the dynamic oil pressure warning circuit board is supposed the
ignore the high pressure switch until the rpms reach 2000 or above so
the wire I cut should not make any difference below that. I was out of
time for the day and did not pursue things any further yet. I don't know
what to think at this point. I may call the seller to ask if they had
been driving around with the oil light blinking for some time. If so,
the leak from the cracked oil cooler o-ring may have been undetected
before damage was done to the engine.

Mark