I have a 2008 chevy impala my engine hot a/c off light keeps coming on but my car isnt over heating some times it fixes itself and its ok i replaced my thermostat sensor 2 times now it only comes on when I use my heater. when the engine hot a/c off light comes on my temp Gage goes right to cold and my heater won't work but then if I turn my air conditioner on it corrects itself somehow but when I turn my heater on it does it again. HELP!