Q: Causes for heater to blow cold air

asked by on

Heater is blowing cold air

Hi...if you are referring to the passenger compartment heater, there are two possible causes of insufficient or no heat. The passenger compartment heater, also known as the "heater core", is essentially a mini radiator and the fluid running through this radiator is the engine coolant. The flow of the coolant into that radiator is controlled by a "heater control valve" that is mounted on the engine compartment firewall. If the valve is stuck in the closed position, the hot engine coolant will not flow to the heater and hence there will be no heat. So, you want to check for free operation of that heater control valve first. The second possibility is a problem with the cold/hot blend door in your car’s HVAC system. Similar to what would happen with a stuck heater control valve, if the blend door is stuck on cold, and thus blocking air flow over the passenger compartment heater, you will not get heat. YourMechanic can readily diagnose your heating system and repair either of these faults for you and would be pleased to do so if you contact us. Thanks for your question.

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. Causes for heater to blow cold air

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: Steering stopped working while I was driving

A recall on Ford Escapes came out in 2014 related to this issue. The torque sensor on the steering column is the likely cause of failure as this has been the case for many other Escape owners. Unfortunately to replace...

Q: My car won't start and the word fuse is lighting up on my cluster. What does it mean?

Hi there. The fuse light will come on if the engine is not starting up for more than 15 seconds. This is a fail safe light that warns the driver that the starting circuit has a fault and needs attention....

Q: Rattling noise AC heater

Hey there, thanks for writing in about your 2010 Lexus HS250h. Even though you said the blower motor looks okay, my guess is that it probably has a bad bearing, which is causing the noise. The only other thing I...

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...
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...