Been having issues with my oil pressure gauge dancing / bottoming out at stop lights after running at speed for 20 mins or more. Gauge reads steady at around 80% until fluctuating. Accelerating boosts it back up. Have oil. Took it in. Mechanics replaced oil pump, oil pressure relief valve, oil and filter. Have pressure confirmed with a manual gauge, but the gauge problem persists. No knocking, smooth running, but it's freaking me out. The shop believes it's the gauge itself that is bad, and is trying to re-establish contact with a firm that repairs them. I questioned if it might be the oil pressure sending unit, but was basically shot down on that. I'm at my wit's end. Any ideas?

 

You are probably right.

There is a simple test to do to verify if the gauge is faulty, but not all folks are aware of it.

 

Can you share what that is? It just doesn't make sense to me that a gauge that consistently reads normally on startup and running for 15 mins., suddenly goes wonky.

 

If you measure the resistance reading at the sending unit at the time it sends possible faulty readings , easier to see with an analog meter, you will get your answer.
I have yet to come across a faulty gauge unit, sending units, yes, a few times so far.
It is quick and not that expensive to just replace the sending unit , especially if you do it yourself.

 

Thanks. I'll bring it up with them again.

 

Getting back to let you know I convinced the shop to replace the sending unit, and the problem is now resolved. After reading up on it, I don't know why the sending unit wasn't the 1st thing tested-- (dammit Jim, I'm just a contractor, not an auto mechanic!) Thanks to you and the local Ford service dept. for confirming.

 

Thanks for the update.