Q: Heater gets hot but then blows cold when idling or driving.

asked by on

heat gets hot then cold when idle or driving i have changed thermastate and new coolant

My car has 45000 miles.
My car has an automatic transmission.

This may be due to a faulty heater blower motor or potentially a bad heater core. As you may know, the heater core is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. To avoid any unnecessary repairs, I would still recommend having a certified expert, like one from YourMechanic, come to your location to diagnose your heater issue firsthand and make the right repair.

Was this answer helpful?
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. Heater gets hot but then blows cold when idling or driving.

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: I don't know how to turn on my fog lights.

The fog light switch is on the left turn signal lever close to steering column the lever rotates to turn on the fog lights.

Q: My engine fan is not kicking in, but my temp is between 80 -100. Is my thermostat bad because my check engine light just turned on

This can be caused by a number of things such a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at...

Q: Car got over heated and won't start

Hi there: Overheating issues can seriously damage the internal combustion engine but also the ancillary electrical parts such as ignition system and starters that help a vehicle start. The only way to pinpoint the exact reason why the engine on...

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 Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.