My oil pessure gauge reads 40lbs when the engine is of and all the way over to the plus side when engine is on.

Could this be the oil pressure switch(sending unit) or the gauge itself?

Thanks,
Schoon[/align]

 

Could be either. The gauge is basically a voltmeter, and the sending unit is just a variable resistor. If you have a service manual, there are tests in there. With the engine off and the switch on, you measure voltage at the gauge. If it is correct, then the gauge is broken. If the voltage is reading too high, then there is a problem with the sensor.

One easy test is to ground the wire from the sending unit. The gauge should read zero. If it doesn't, then the gauge is most likely bad. If the gauge is reading 40 with the key turned off, I'd guess a bad gauge.


bill.

 

Hey Bill,
Would you believe they don't make new oil pressure gauges for 74 Vettes. I need to send mine in and have it rebuilt.
Schoon

 

Did the 74 oil gauge go to an electric one or is it still mechanical with the plastic tubing going to the back of the engine?

 

It's electric. I think 74 was the year they switched.

 

Wow, that's a bummer. I could only find 75 and newer, and the old "tube fed" oil pressure gauges aftermarket (new).

bill.