WTony

I installed the aftermarket rally pac in my 442. Went through the repainting internals to match and now have the correct illumination. Also there were no surprises with the temp gauge reading too hot when the car is at normal operating temp.
The oil gauge was operating normally for about 4-5 days but suddenly went all the way up when running. When I turn it off it goes back to quarter to half way like it was before. Now, I fiddled with the connection on the sender and that didnt make a difference. When I disconnect it its still all the way up. When I reconnect it it doesnt move.
My understanding is if it were a bad ground, I'd have no lights, and the temp gauge would be messed up as well? Could this be a bad gauge or possibly something else causing it to read full pressure when the car is running?

oldcutlass

You have a bad connection between the sender and the gauge, or a bad sender. Your gauge is looking for ground through the sender.

WTony

I'd almost bet on that cheap azz aftermarket sender having gone bad. Is there a way to test the ohm's to see if its working correctly?

BlackGold

Is the send unit well grounded to the block? In other words, you didn't use teflon tape or some other sealant when you screwed it in, did ya?

WTony

BINGO. Yes I did! I will eliminate it and see if it comes back to life!

oldcutlass

If removing the Teflon tape does not fix it, I'm thinking a 200 ohm potentiometer should work to test the gauge. I think the range is from 10-180 ohm.

WTony

I didnt think Teflon was the issue at first. I had continuity from ground to the body of the sending unit with the signal wire disconnected. I also have continuity from the connector of the sending unit all the way to the post on the back of the gauge.

But, Just because it was asked here and I said I'd remove it, I took the teflon off the sending unit and the elbow where it goes into the block and...........
WA LA! It works again!

Thanks for the help guys!

oldcutlass

Well done.

Miles71

I am surprised the Teflon tape was the issue.
I have often used a single layer of Teflon tape on both the Oil-Sender and Temperature-Senders with good results.
I have never had any issues with just using 1 single layer of Teflon tape.
I will clean the threads on both sections thoroughly and remove as much rust and gunk as practical. Then apply just 1 layer of Teflon tape.
The theory is, that as you screw in the senders, some of the threads will rip through the thin-tape and make metal-to-metal contact and provide a reliable ground.
I am glad you solved your problem.

oldcutlass

Since it's pipe thread, the threads will seal themselves. If you want you can use plumbers thread sealer (pipe dope) with Teflon.

citcapp

The Teflon pipe dope works great and leaves the ground in tack