oil pressure gauge

[jwt73]

Hello porsche knowlege people,
I just finished doing my valve covers a few days ago (1987 911), and now I noticed that my oil pressure (gauge in dash) is pegged at > 5, and I don't know what to do? It does go down to off position when the car is switched off though. Upon starting it, the gauge reads > 5 and just sits there and doesn't vary with RPM's. Does anyone have any ideas on how to diagnose it or what to do?
I appreciate any and all help offered.
Thank you,
JWT

[Crude Rudy]

your circuit is open. when the connector is not properly attached or the wire is broken the gage is pegged. try pulling the connector off cleaning the contacts, make sure the small gage wire is not broken and the female connector is closed down enough to make a tight contact.

[jwt73]

I cleaned all contacts, and still no working gauge. I then tested wire continuity from the back of the gauge to the female plug that attaches to the oil pressure sender, and there was continuity. I suspect that based on the fact that the gauge pegs with the ignition on regardless of whether the wire is attached to the sender or not, that the problem is in the gauge. Does this sound correct?
thanks

[Walt Fricke]

No, with the sender I'd guess. Here is how one works.





So if one of the resistance wires breaks near the low pressure, low resistance end of things, it will act like a break in the wiring.

To check, put an ohmmeter on the gauge (with wires disconnected) and rev your engine. You should see a smooth change in resistance from very little to some kind of peak.

You can check your gauge by grounding the sensor input. If it still pegs, then perhaps the gauge has a faulty ground.

Or maybe (my last choice) the gauge is broken internally.

Walt Fricke

[jwt73]

Walt was right again.
It was the sender. As soon as I had installed a new sender, and cranked it up, the little gauge works again. FINALLY.
Thanks Walt, you are quite the genius.
Jonathan