Temperature gauge mystery (to me, at least)

[CheeseSteakJim]

Freaking temperature gauge is pegged full-hot all the time. If I unplug it from the sender, it'll go down to around the RM in NORMAL. This happened to me early in my ownership of the car, and I replaced the sender. It happened again after a couple days, and I got the store to exchange the sender as a defect... lasted for quite some time after that. Several years, I'd say. It's been dead for a while now, though. Recently replaced the sender again, to no avail. Should've tested the old one before going and spending the money, but I was lazy.

Does anyone have any ideas, or anything I can check? I would guess it's a short, except it responds when you unplug sender on the intake manifold... it just doesn't respond how it should. According to my EVTM it's a straight shot from the gauge to the sender without even connectors in the way, so that doesn't really give me many ideas on what to look at...

[Southern_Pride]

Probably a bare wire running through the firewall or in the dash. Or a corroded section.

[sly]

I had this issue with that Pontiac Parisienne I had. bad ground on the gauge itself. once I fixed that... it worked for a while again... the next issue was the sending wire itself. Looks like your sending wire is good though. Probably the ground wire fell off the gauge or the harness to the cluster is loose.