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

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: Car heating

Hi there. There are two tanks usually next to each other that can cause some confusion. One tank is the windshield washer fluid reservoir, the other is the radiator overflow tank where you add radiator coolant. However, if your car...

Q: stuck in first gear

For this issue I would first recommend having your transmission inspected by a certified professional. There are a number of things including faulty shift solenoids, low fluid level, or catastrophic damage that could be causing your transmission to have these...

Q: Engine Overheating after 20-30 minutes. Why?

Hi there. One of the easiest ways to test a water pump is to carefully place your hand on the lower radiator hose while the motor is running. Two things should happen; first, as you suggested, the hose should feel...

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 Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...