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For some time now (years) ive been dealing with an oil pressure gauge that works when it wants to. For the first about 18 of the 21 years ive owned mine it worked fine. Over the last couple of years ive replaced the sending unit about 4 or 5 times. Ive read replacement quality is sketchy. Ive also done a new printed circuit board, a used replacement gauge and a new pigtail at the sending unit becuase the wire had an amost worn though spot on it. Keep in mind i hadnt touched a thing when the gauge was working fine, i only started trying different things when it started acting up. What are y'alls suggestions as to how to tackle this? I do still have the original gauge that i replaced. Can i run a wire from the sending unit to it, and then a good ground and try that? I my head it seems like that should work. Also, every time i turn the ignition key to run, the gauge drops as low as it can go, technically reading below 0 then. Once i turn the key off it creeps back up to exactly 0. Key off after sitting a couple of minutes Key on it moves to here, every single time, without fail.
OK. Not certain how much help I can be. First. Getting a replacement sending unit that reads correctly and actually lasts seems to be impossible. My original sender lasted over 40 years. When it died. I bought one that was junk out of the box. Then I bought a SMP sender. It actually read correctly, for about a month. Then my gauge pegged. I have tryed a couple more. The one in my car now works. But reads high. At least it works and I know by how much it reads high. So, other than that my gauge works as it should. Original gauge in center cluster and original wiring.
Key off, for about a week. Notice how this gauge and others stay frozen on the last reading when car was shut off. Temp is not 180. But was when I turned off the key a week ago. Oil pressure still shows 40 PSI. Yet engine is cold. Key on. Not started. Oil pressure shows a tad below zero. Actually I never really noticed this before. Temp gauge dropped down as well and volt gauge comes up to voltage. This is normal.
If I were you. I would pull the wire off the sender. Just.let it hang disconnected. What happens to your gauge then?
Once again, not certain how much help. But at least I can show you normal.
Basically, if your wire is disconnected from the sender. If I remember correctly. Your gauge should read zero. And if you connect the sender wire to a good ground. It should peg.
I just ran mine up the road to check the tires and fill the tank to get ready for tomorrow's club run. Here's some pics when I pulled back into the garage. Sorry for the glare. Garage door was still open.
Printed circuit boards are not what they used to be. My wiring is over 45 years old now and has a few internal breaks, gages are old too, my second GM clock has quit on me again, available senders are pretty scketchy......so.....I give.
My plan is to fill the whole center cluster with an aftermarket solution. There are at least 2 companies ready to take my money for direct replacement aftermarket solutions. Time to just move on is my opinion. JMO.
Intermittent 79 factory oil pressure gauge
