Recently our oil pressure light has been flickering and sometimes staying on
steady for seconds at a time.  I have checked the pressure by pulling the
0.3bar switch and installing a pressure gauge.  I have 7-8 psi
(0.48-0.55bar) at idle and 30-40psi (2.00-2.76bar) at 3000RPM.  I have
noticed the light flickering both below and above 2000RPM.  The light is
never continuous above 2000RPM and the low oil pressure buzzer never sounds
not even a short BZZT.

Another bit of information is that I run 20W-50 during the summer months and
10W-40 during the rest of the year.  If I wait too long in the spring to
change over this problem appears.  The problem also arises during the summer
if I have been driving for extended periods of time when ambient air
temperatures are at or above 95 degrees.

Last summer I had our mechanic replace the 0.9bar pressure switch.  I
understand that VW also has a 1.8bar switch and that this switch is
sometimes installed by mistake.  If my mechanic installed the 1.8bar switch
this would explain why this problem appears when the oil viscosity is too
low either due to ambient air temperatures or viscosity breakdown due to
high temperature duty.  But if this switch is the cause then why is the oil
light illuminated below 2000RPM?  And, why don't I hear a sound out of the
oil pressure warning buzzer above 2000RPM?

My other theory is that the wire going to the 0.3bar switch is grounding out
someplace.  This would create a momentary oil pressure fault for what ever
duration the grounded condition existed.  This would explain the illuminated
oil pressure light below 2000RPM but not above.  As I understand it the
0.3bar switch input is ignored above 2000RPM.  Has anybody confirmed this by
grounding the switch and running the engine above 2000RPM?  If a grounded
wire is the cause of our problems then why does changing the oil temporarily
eliminate the problem?

Thanks in advance,

Tom Moritz

[text/html]