Skip the auto shop - Our mechanics make house calls

Q: Heater blows hot for 10 minutes, then it blows cold.

asked by on

When i run my heater it blows hot for 10 minutes or so, then it blows cold air out of the defrost vents. If i turn it off for about 10 minutes it will blow hot again for again about 10 minutes and then blows cold again out of the defrost vents. If I am running defrost it is basically the same hot for a little while and then cold untill i turn it off for a little bit.

My car has 118000 miles.
My car has an automatic transmission.

Hello, thanks for writing in. This problem could be either an engine thermostat that is not keeping the engine at a constant running temperature (temp gauge steady in the center), or the heater control valve or controls are malfunctioning not allowing engine coolant into the heater core (passenger compartment). It is also possible that the heater controls are allowing cold outside air to "blend" with heated air by not closing one of the ducts in the HVAC unit. I would recommend having a heater inspection completed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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: My car is over heating and blowing cold air.

The heater not working in some cases may be related to the overheating problem you are also having. This may be due to a faulty heater blower motor or potentially a bad heater core. As you may know, the heater...

Q: If a timing chain isnt put on right can that stop the car from starting ?

Hello, thank you for writing in. You are correct. If the timing belt is broken, installed wrong, or the engine is off time for any reason, the vehicle may not start. If you have had recent repairs made to the...

Q: Air conditioning doesn't work

You will have to start with an A/C service. An A/C service will recover your old refrigerant, pull a deep vacuum on the system, and check for leaks, if there are no leaks, the system will be filled to the...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...