my 3s hatchback(75k miles, so not too long on coolant for factory fill) a/c got warm for a second so i looked down at my gauges and noticed the temp was slightly high and moving up, slowly. turned the a/c off and it helped some, however it started going up again later. so i turn the heater on and it goes back to normal operating temp. and stays there seemingly as long as i want to drive. so i get home and check the fan as i thought that was the issue, but the fan is on all the time with the a/c as it should be and it comes on as the car gets warm as it should. so fan is ruled out. car is not leaking any coolant nor is it low. put a new radiator cap on it just to be sure(as i had a radiator cap do something similar on an old car, and its a cheap fix) and nothing. the water pump is not making any noise nor is the belt, the belt is new( changed last month) and deflection is fine. so today i noticed it will be at regular temp for awhile(5 to 10 miles) then start climbing until i turn on the heater then if i tun the heater off it goes back up fairly quick. i am almost 100% sure thermostat is the cause but just running it by the forum before tearing into it, as the thermostat is in a pain in the ass spot on this car.
any other ideas, or suggestions on things to look at? or just replace thermostat?
any other ideas, or suggestions on things to look at? or just replace thermostat?
