okay, i just bought my V6 1998 camaro and for some strange reason the temp gauge keep slowly moving up then back down and does that the entire time im driving (while sometimes "overheating") when i stop to check then engine feels like its at the normal temp. i just replaced the thermometer and radiator but it continues to do it. my guess is it has something to do with a short in the electrical but i dont know to much about cars other than the basics. can anyone help me out?

 

you mean the thermostat right? mine did the same thign but it really was overheating.
Does it use up coolant Abnormally fast?
maybe it is the sensor

 

It usually moves like that when it's low on coolant. Check for leaks. Has the intake manifold gaskets ever been replaced? Common issue among GM coolant leaks. Replace with the better Felpro gaskets. In order to get all the air out of the system I know the front wheel drive 3800's have bleeder screws on the thermostat housing. You need to do this while it's running. Crack the bleeder screw open and top off the radiator.Close the screw when no more air is coming out.

 

would that also explain why the car's heater blows cold air when its "overheating" and then suddenly blows hot and then the car cools down?