Oil and pressure

[chasrb]

Here is some background. Driving a few months back I noticed that suddenly my oil temp was pegged high and my oil pressure was non-existent! Right after I noticed the readings, I pulled into a gas station, checked the oil levels, they were good, turned off the car and let it cool down for 30 min.

When I got back in it was dusk, I started the car, the reading had dropped to mid temp range and the pressure was 2 bars or so. I turned on my lights and when I did the gauge pegged in the red for temp and bottomed for pressure. Strange. So I turned off the car and turned on the lights, the gauge lit up, I then started the car again, the lights went off and the same pegged symptom happened.

I have driven the car little in the last few months since it is cold, I have pulled all my instruments out checked all the wires, swapped out the illumination lamps for LED and reassembled it all.
I check the instruments - all light, when I turned the ignition to start, the oil temp/press gauge lights turned off and the temp pegged hot and the pressure stayed at the bottom.

I ran the car for a while lights off, the temp moved into the 3/4 hot range in about 15 min and the pressure never moved.

So I am really perplexed on this. It happened suddenly while driving one day. I have not checked to see if oil pump is working, not sure how actually. The oil press sensor was replaced a year ago so I would think it is good.

I can take the car to my mech, but I'd really like to find out the cause and repair it myself it at all possible.

So any of you have any similar stories and resolution to the problem?
Cheers,
Chasman.

[Charles Freeborn]

Without the wiring diagram in front of me, and knowing the year and model it's hard to say exactly , but it sounds like you have a short between the lighting circuit and the gage. The fact that it's both gauges in a single cluster points to the Robles bent in the gauge, or under the dash somewhere, rather than engine compartment where the sending units are. Sorry to be vague, but electrical shorts can be a stinker to chase down. Start with the ground wires and go from there.

[Guardsred911]

I have an'80 sc and had a similar issue. Turns out I found the issue quickly due to the good folks here who suggested I check the wiring harness in the engine compartment on the drivers side near the voltage regulator. It was loose and I pushed it back together, problem fixed! I don't know what car or year, but check that. And report back pls! Good luck!

[chasrb]

I'll go look in the engine room!! Thanks

[E Sully]

A loose or corroded chassis ground would also create problems.
Behind the instruments is a common ground point with several brown wires on a stud.