[Vwdiesel] Oil Pressure Warning System on '84 Rabbit

[LBaird119 at aol.com]

  The low pressure switch is in the really low range indeed, 
about 4 ish psi.  The high one is roughly 20psi.  
  If you're below 2K rpm, the low one is the switch that 
is used.  So long as you're above threshold pressure then 
the light won't come on from any speed from roughly 2k rpm 
to idle. 
  Once at the higher rpm threshold is achieved or exceeded, 
the higher pressure switch comes into play.  If your pressure 
is over that switches trigger point, at any rpm above ~2k rpm, 
then all will be happy. If at any speed above threshold, the 
pressure is below the set amount, the light and buzzer will 
sound.  It will keep buzzing until the rpm drops below roughly 
1200rpm AND the lower pressure is still exceeded.
  Generally the higher pressure will sound near the rpm threshold 
just as the lower pressure switch tends to go off at idle simply due 
to engine speed's relationship to oil pressure.
  There is INDEED a bypass in the oil system.  It's in the pickup 
piece of the oil pump and for some unknown reason VW likes 90psi 
give or take instead of most domestics in the 40 psi reigon.
     Loren