Q: Car will overheat if I don't have the fan on. When fan is off it doesn't come on to release heat from engine. So the fan is always on.

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So when i drive my car i have to have the fan constantly on. If not it will tend to overheat. And every time i check the fluids the reservoir tank for the coolant always seem to be full or seems like overflowing. I noticed that when the fan is off it doesn't usually come on automatically to release heat from the car like its supposed to thats when the car overheats. Only when i have the fan on med or high fan it goes back to normal. There is new sensor new thermostat and new radiator. What else could be the problem to this?

My car has 133000 miles.
My car has an automatic transmission.

Check the wiring to the coolant temperature sensor and see if there is power to the sensor switch. If there is no power, then check the cooling fan relay and see if its clicking on. If there is no clicking motion, then remove the relay and check for power to the relay. If there is power to the relay, then the cooling fan relay needs replaced. If there is no power to the relay, then check the fuse. If the fuse is burned, replace the fuse. If the fuse is good, then check power from the fuse to the main circuit on the fuse box. If there is no power, then the fuse box needs replaced. If the fan comes on with the air conditioning system switch turned on, that is because the switch overrides the cooling switch to make the condenser cool down to make the air conditioning system work properly.

If you need further assistance with your cooling fans not coming on when the engine gets hot, then seek out a professional, such as one from Your Mechanic, to help you.

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