[urq] Oil Pressure warning system

Maurits Jonkergouw urquattro at moregraphics.nl
Tue Apr 6 08:27:38 PDT 2010


Because I could not find the proper 234 oil pressure relay (P/N 857 919 082), I've replaced the (suspect) 2-pin large pressure sensor with the 1-pin white 1.8 bar switch.

Because of this 'new' switch I had to put in the 240 oil pressure relay from a Coupe GT, which works fine (disabled the buzzer).

Everything works fine while driving, except when I completely stop the car (RPM drops below 2000), the oil pressure also drops below 1.8 bar and triggers the oil warning light briefly and thus triggers the voice computer "Achtung, Olstand prufen" message.

According to the diagram from the Coupe GT, the 1.8 bar switch (F1) connects to terminal 2/OES of the 240 relay and is 'wire-compatible' with the original 234 relay carrier (2/G).

Although terminal 6/La from both relays is the same on the relay carrier, on the 240 relay, 6/La is connected to a second 0.3 bar switch (F22) and triggers only the oil warning light K3 - while 6/La on our 234 relay is not connected to a second pressure switch - but instead triggers both the oil warning bulb K3 and voice computer J129.


Question: is it normal the oil pressure drops below 1.8 bar on fast decelleration and <1500 rpm or idle? 

If so, should I better replace the white 1.8 bar switch for the black 0.3 bar switch if I want to continue using the 240 relay? 

0.3 bar seems pretty low for a warning? I can imagine if you are doing 60 mph and the oil pressure drops to 0.3 bar, it's pretty too late?


Thanks again.

Regards,
Maurits

1986 quattro GV (rebuilt)


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