Skip the auto shop - Our mechanics make house calls

Q: Heater only works on high. Heat is not hot.

asked by on

Car takes awhile for the heater to blow hot air. It only works on high. The air is not that hot.
My car has an automatic transmission.

If your heater only blows when the setting is on high, this may suggest that you have a faulty blower motor resistor. The highest speed setting may still work because in most cars in the highest fan speed settings the current bypasses the blower motor resistor. In some cars, if the resistor is failed, the fan may stop working completely. Another reason a blower motor resistor may fail is when the blower motor has a mechanical problem or when a foreign object jams the blower motor fan blade and prevents it from spinning freely. This leads to increased current through the resistor and causes it to overheat and fail.

The lack of heat being generated by your system may indicate a faulty heater core. The [heater core]((https://www.yourmechanic.com/services/heater-is-not-working-inspection) 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. I would suggest having an expert from YourMechanic come to your location to diagnose your heating system.

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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 stuck in 3rd gear

Hi there. When a professional mechanic is hired to diagnose a problem, the trouble code(s) are only one part of the complete inspection. In many cases, the codes, like the P0760 code you've listed, indicate a possible source of a...

Q: thinking of buying a truck with 300K miles,well maintained etc. would it be a good idea?

The thing to look at is this is a full size truck with a small V6 engine size. This engine would have worked harder than a larger V8 engine would have. This does not mean the engine is bad but...

Q: Timing belt off track

A timing belt that appears to be slipping its way off its gear, or coming off track, is an indication that the timing belt is loose. When the timing belt starts to slide off its gears, it can rub against...

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...
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...
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...