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Q: Heating unit makes my temperature gauge go up

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Car runs well but when I run the defroster or try to warm up the inside of my car the tempurere gauge goes to the over heating side when I turn off the heating unit gauge goes right back to normal and car runs well
My car has an automatic transmission.

Hi there. It sounds like there could be the possibility of a low cooling system level. Check the level when the engine is cold and add as necessary. When you turn the climate controls to heat the inside of the car, coolant is diverted to the heater core to use the heat in the coolant to warm the air as it passes over. If this is producing an unusually low level in the cooling system, the coolant temperature sensor may act erratic as it would trying to measure temperature of a limited supply of coolant. Note that air heats faster than water and the sensor could be reading the air in the system.

I strongly suggest acquiring a qualified technician to perform an inspection and avoid replacing unnecessary parts. YourMechanic has several technicians available that can assist you with a cooling system inspection and provide an estimate and direction of repair.

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