Factory Oil Pressure gauge goes past 60 psi

[jkk]

Hey Guys,

The OEM oil pressure gauge was working fine showing about 40psi. Then started going to 60 then past that. Disconnected the oil sending unit still the same. Will slowly go back to 60 but when the key is on goes past 60 again.

Any ideas bad gauge?

Thanks for any info

[ray_mcavoy]

The '78 & newer electric oil pressure gauges operate very similar to the fuel gauge. With zero pressure, the sending unit should be near 0Ω. And at full pressure (60psi) the sending unit should be near 90Ω.

If the sending unit is bad (open circuit) or disconnected (also open circuit) it will make the gauge peg beyond 60psi. So simply unplugging the sending unit doesn't give you any valuable diagnostic information. However, if you take the disconnected wire from the sending unit and temporarily short it to ground, it should make the gauge read zero if the gauge & wiring are okay. And if you have a multimeter, you can set it to the resistance / Ohms scale and use it to measure the resistance of the sending unit (unplugged from the gauge). It should show somewhere between 0 to 90Ω depending on the oil pressure. If the reading is considerably higher (or completely open circuit) the sending unit is bad.

[jkk]

Great info thanks will check it

[70GMCer]

My 83 is doing the exact same thing. I will try those tests....

[bennylava]

If you end up going with a replacement gauge, just make sure its maximum is 60, not 100. I got an autometer that goes to 100, and the only time I can ever see that there is any oil pressure, is when the engine is cold. My mistake.

[jkk]

I grounded the wire going to the gauge and it went to zero so I will replace the sending unit and see what happens. Will update the results.