My Temp gauge seems to be very eratic. When I drive the car the gauge is fine. When I stop or put the car in park for a minute,the rage goes through the roof. When I turn the car off then on again,the temp gauge resets to give me a normal reading. The other day I also noticed the gauge running hot while driving up-hill,when I started going downhill, the gauge went down again,and gave me a perfect reading, once I was driving on a level surface. Is there some sort of ballast that may be malfunctioning,or possibly the Thermostat control sensor? I changed out the thermostat so I now it's not there