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