Skip the auto shop - Our mechanics make house calls

Q: Heating unit makes my temperature gauge go up

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Heating unit makes my temperature gauge go up

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: OVERHEATING

Be sure not to drive the car if it is overheating because overheating can warp the cylinder head and/or engine block causing costly damage. With regard to the temperature sensor, the only guaranteed way to avoid diagnostic headaches is to...

Q: Puddle of fluid

If the fluid is pinkish or red, it could be automatic transmission fluid. A certified technician from YourMechanic could perform a leak inspection and let you know what the required repair is. The temperature fluctuation you refer to is probably...

Q: When backing up, my car makes a rocking noise.

The noise is the parking brakes are out of adjustment and the brakes are dragging. Check the rear brakes and see if they are releasing when going in reverse. If you need further assistance with your brake system, then seek...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.