engine and drivetrain Temp Gauge pegging "hot"....do I need a new sender

[02fanatic]

Hugo has had this problem before & then it went away....I don't know if it's the sending unit or the wiring. The wiring is original at the sending unit plug & it's corroded and sort of half attached, but connected I think.

When I unplug the sender the gauge reads cold (dead). When I plug it in again the needle on the gauge pegs full hot...this happens when the engine is cold and not even running.

I just don't want to drive it this way in case it really "does" get hot. I don't have a temp sending unit, just volts, oil pressure & oil temp.

What do you think the problem is...wiring/short? or the sending unit? I don't want to remove the sending unit and get coolant all over the engine unless absolutley necessary.

Opinions???

Thanks,

John

[Jack]

John, this is exactly why I put in the VDO's (OT, OP, V) on the 72. I've got a new sender, new wiring and new grounds and the gauge which tests out ok is still in the red. Mike P suggested removing the cluster and running a dedicated ground from one of the screw on the back of the gauge board. I've not done it and won't until I put the car up for the winter. For now i'm using my infrared gun and oil temp. ONe thing on the sender. It grounds thru the water neck. That connection corrodes badly. Hope you don't have to drain it. I'm in the same boat on the draining. I guess I need a drain valve on the bottom of the radiator.

[DavinSF]

I've gotten all kinds of batty temp gauge readings until I did the extra ground. It's been dead-accurate ever since. Check the archives for a description and pic, but in short you remove the gauge cluster and run extra wires from the round posts at the back of the temp and fuel gauges to ground. Super simple and saved me a lot of headache when trying to troubleshoot a cooling system that was actually working perfectly. Cheers!

[02fanatic]

That sounds like a plan! Many thanks for reminding me of that "fix". I don't even need to use my lift for that fix...

"It's always somethin!" (as Gilda Radnor used to say on SNL) :-)

Thanks,

John

[ccr2002]

i did the same thing when mine had the pegging hot problem...it's been perfect ever since...just wired the two screws on back together and then to ground...

good luck