View Full Version : temp guage

01-12-2017, 09:26 AM
I have a 90 sc that has a temp guage problem.I tried 3 new sending units ,and tried grounding wire and it shows hot . what is going on?

01-12-2017, 10:43 AM
It shows hot when you turn the key on when you know the car is stone cold? Or does it warm up to the hot temp?

If i warms up to the hot temp you need to check the thermostat, radiator, fan, head gaskets....

01-12-2017, 01:11 PM
We had a problem with the temp gauge on our silver '90 SC. I put a new sending unit in when doing the head gaskets. Turned the key on and the gauge went to zero. Started the car and the gauge immediately all the way to hot. Turned out the parts place (Advance) gave us the wrong sending unit. Apparently we got one that wasn't for an SC.

Eddie & Breanna Donato
'90 5-speed SC highly modified
'90 auto SC stock (except for double intercooler)

01-12-2017, 01:23 PM
What does 'shows hot' mean? Pegged, or just worrisome, or? Sudden change or over time?

There was a TSB (years?) that stressed matching senders with gauges...the original issue was customer concern that the car was running hot, so Ford apparently recommended to dealers when those complaints came in to replace both (matched), with the effect being appearance to help reduce worries and perceptions.

Today, senders seem to have fallen into general application where matching is not a priority so that stocking levels can be trimmed.

In this case, tho, it sounds like a circuit issue that new senders won't cure. I'd check grounds on the cluster and consider swapping the temp gauge. As well, checks with an IR temp gun can help determine what the actual temps/actions are under the hood to help reduce tail chasing in the process.

Do you have an EVTM for your car?

01-13-2017, 09:03 AM
The car gets up to temp,but the gauge shows just off cold .If I ground the wire it will go to hot,sorry I didn't word it right

sam jones
01-13-2017, 09:29 AM
Good morning

Check the oil pressure sender connector. It might be oblong and loose fitting. I've had this happen a few times. You could squeeze the connector with pliers and hope for a tighter fit or find a

suitable MN-12 replacement at the your local salvage yard. Try search.



Good Luck.

01-13-2017, 10:51 AM
The car gets up to temp,but the gauge shows just off cold .If I ground the wire it will go to hot

My '90 Anny had that very same issue when I first got it. Turned out the push-on connector at the sender was corroded (green inside), and loose fitting. I scraped/cleaned it out so you could see the brass/metal inside, then squeezed it down a bit so it fit tighter when pressed back onto the sender stem, and the gauge went back to normal operation. I've heard some cases, where a new connector was needed, instead of just cleaning and re-sizing.

Also be sure the sender is able to make a good ground path to the standoff/thermostat housing. Use as little thread tape/sealer as needed when installing.

Still no joy, be sure to check the grounds on the engine...make sure the ground cable from the pass. side motor mount over to the body is clean, not green at the ends. Might need replacing if original.

Good luck.