I pulled my hair out on friend, Julie Olsens, Syncro camper just after I
installed a new engine in her bus.
    First a brief explaination of how the system works.  The system has
two sensors.  Sensor one, is located between the pushrod tubes of number
3 and 4 cylinders.  This sensor is grounded when the oil pressure is
under about 7 pounds.  This turns the light on when the key is on but
the engine is not running.  Sensor two is located under the water pump
between the oil filter and oil pump.   This sensor is grounds itself out
at pressures over about 18 lbs.  There  is a control unit mounted in the
speedometer and it also senses engine RPM.  THe control unit looks for
system pressure from sensor one up to 2000 RPMs.  Then the control unit
looks for sensor 2 to be grounded out. (a quick test to see if the
sensor is working, hook a test light to a power source and then probe
the wire from the sensor, rev the engine briefly,  the test light should
light)  As soon as the control unit looses ground from sensor two and
the engine RPMs are over 2000 the light goes on and the buzzer flashes.
    Now both sensor wires run to a connector near the thermostat
housing.  On julie's bus it was wire tied to the coolant hose.  This
cause fatigue on the wires from 170 thousand miles of engine movements.
A couple of new connectors cured her problem.  I'd bet the same for
you.   Good luck.
--
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         LiMBO, The Late Model Bus Organization, international
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