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Username Post: Oil Pressure Diagnostics - Electrical Help
Posts: 7

Reg: 09-02-21
09-26-21 06:53 AM - Post#2827978    

1980 C20 350 w/TH350c - 100k miles

My C20 oil pressure gauge is reading low at idle and when driving. It fluctuates slightly but stays below the first has mark (15psi?). I removed the sending unit and did a continuity test. It had a static 16ohms resistance. My expectation was that it should read infinity. I purchased a replacement oil pressure sending unit. To establish a baseline and compare it to the old unit. I measured the resistance and was getting about 1.6ohms. Again, my assumption is that there should be no resistance when the unit is out of the vehicle.

Question: Is my assumption correct that an unplugged and deinstalled sending unit should read infinity?

I also tested the wire that runs from the sending unit back to the wiring harness on my (new) circuit board for the gauge cluster. My expectation was that I should have zero resistance. I did not. There was a small amount of resistance registering on my Klein voltage meter.

Question: If that wire casing is bare and touching metal, or crushed in some fashion would a small amount of resistance register?

The engine sounds fine. There's no knocking. 5w30 level is right on the mark. I am going to try changing the filter to see if there is any difference. I really would like to verify whether my gauge is reading correctly or do I actually have an oil pressure issue.

Thanks in advance for any help anyone can offer.
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