Skip the auto shop - Our mechanics make house calls

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?

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. 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: Burning smell from fuse box

An electrical burning smell coming from the fuse block is never a good sign. Your fuse block is a major junction in the supply of power to most of your engine management system and accessories. A proper inspection should be...

Q: Truck not starting consistently

Hello. First, I am assuming your vehicle has an issue with the starter. Voltage drop testing should be performed between the starter and the battery. This will tell you if the is a loss of contact between the battery and...

Q: Heat in the front won't work

Hi there. The front heater core my be restricted. A cooling system flush may resolve the problem. It may be a faulty temperature blend door actuator if the blower motor is still not operational. Checking the fuse would be in...

Related articles

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...
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.