The temp gage on my 1985 El Camino pegs cold when the car is started. When the car is off the gage shows a temp indication. I just took it for a 20-min drive and the gage reads about halfway b/t 100 & 220, which seems reasonable. As soon as I put power to the car, it pegs cold again.
I’m no mechanic, but that seems to me like a ground or a short somewhere. I have the Haynes manual but it’s not super helpful on this subject. Any tips?
This sounds like fairly normal gauge operation to me. Many older cars will allow the gauges to fall where they may when the car is off. When they have power is when they start working. If you had a power or ground problem, they wouldn’t work at all or would work erratically. It sounds normal and reasonable to me.
Key on it pegs cold, key off it reads normal
Whats it do when you remove the wire from the sender?