Ratty Data?

[Surfer]

I thought I had a overheating problem, but noticed when I shift the temp goes up 40 of 50 degrees, and when I turn the key to off, it peaks to 240 and stays there for awhile when I restart. What kind reading should I get to test the sender (variable resistance, variable voltage)? Could it be a grounding issue, bad temp guage? Any ideas.? Oh yea, Chev 350, about 1985.

[marcdups]

Surfer, sounds to me like you have a short somewhere either in the sender, guage, or wiring, what I would suggest, with the key on remove the brown/ blue wire from the sender and ground it to the block, if the guage pegs, it should be fine, I would replace the sender then, if that does not work then it is the guage or wiring harness.