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!
  1. Home
  2. Questions
  3. Heater only works on high. Heat is not hot.

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 overheated while idling. What is wrong

There are a few faults that will cause your 2013 Hyundai Elantra to overheat when idling. The most common would be the electric fans not functioning. When air is flowing over the radiator the car works fine, but when the...

Q: SERVICE ENGINE SOON LIGHT IS ON

Your service engine light is programmed to come on at specific mileage intervals based upon recommend services. You do have a window of time when this light comes on in that you can continue to drive it for a short...

Q: Shift link or Axle issue

Hello. From what you've described it would appear that your vehicle may have suffered serious transmission issues. Slipping and grinding sounds are commonly associated with internal transmission issues. It may be possible that the torque converter or transmission gears have...

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...
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...
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.