Temperature Going Hot then Cold

[amd25]

I have a 1992 SC Coupe and the Temp runs hot. I had it checked out and the mehcanic said that he could not find anything wrong. He took a temp reading while the temp guage was on "H" and he said it was 209. The car has never overheated. Any ideas. THe other thing that is happeneing is when the air is on and the temp guage goes to "H" the air gets warm. When it temp guage gets cooler drving at a high speed the air is fine. But the temp keeps going from 3/4 to "H" and it affects the air everytime this hapens.

[sierrap615]

replace the ECT with the new redesigned all-brass sensor ( buy the OEM from a saturn dealer ), if it still runs hot, replace the thermosat

[Joelb251]

The ETC or CTS (coolant temp sensor) do tend to crack over time if they are a nylon design, the brass one will help if the reading is off on the gage, before replacing it, might as well check the connector for it, if the connections are green, it is leaking and might as well replace the 2 wire connector too since corrosion will change the gages accuracy too. To me it sounds like it running hot, as if the thermostat is sticking.