Why is My Car Heater Blowing Cold Air? Simple Ways to Know What’s Wrong with Your Vehicle’s Heating System

With the coming of the cold weather, it is certain that you’d use your car heater to warm up your car from inside. But, what if your car heater blows cold air or stops working altogether? In such a case, you can ask yourself why is my car heater blowing cold air.


A faulty car heater can irritate you when you find it out on a bitterly cold winter day. An unreliable car heater can make the cold winter days almost intolerable. A car heater can fail in varied ways owing to a few problems. Just like a home heater, an automotive car heater has several parts in it that work together in order to blow out hot air.

What is a Car Heater?

An automotive heater core is a device similar to a compact radiator that is made up of aluminum or brass tubing. It is useful in heating the interiors of a vehicle through the tubing that transports the hot coolant, in addition to the fans that spread the heat emitted by the coolant.

The hot coolant is passed from the engine of the vehicle to the core’s winding tube, which acts as a medium between the coolant and the cabin air.

The core tubes are equipped with fins, which augment the surface for transferring the heat to air that is forced past them via a fan and thus warms up the car’s interiors. A heater core looks after the heating and defrosting actions of a vehicle. It is generally located directly at the back side of the car’s dashboard.

How Does a Car Heater Work?

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A car heater makes use of the heat in the coolant, which flows around the engine of the car. This is why the car heater only blows hot air when you run your car for a few minutes since then it will warm the coolant inside its engine.

The water circulation is regulated by a thermostat, which rests for some time till the water arrives at a specific temperature. And, when it does, the thermostat allows the water to flow in order to cool the engine of your car and thus warm your car heater.

A car heater takes some time for blowing out warm air. The heater cannot blow heat until the engine of the car warms up. In order to heat up the interiors of your car, you require:

  • Sufficient amount of water in your vehicle’s engine
  • A running heater and heater controls
  • A functional thermostat
  • A leak-free cooling system

Why is My Car Heater Blowing Cold air?

There can be numerous underlying reasons behind the failure of your car heater owing to which your vehicle might be blowing out cool air instead of heat. Some of these reasons include:

  • Insufficient amount of coolant in the car engine
  • Issues with the heater core like a plugged one
  • Broken or blocked heater buttons
  • Stuck thermostat

Now, let us study these issues in more detail so that you can have a better idea as to what you need to fix in a case of a faulty car heater that blows out cool air. I’ve found this helpful video so that can fix your car that does not blow hot air.

1. Insufficient Amount of Coolant in the Car Engine

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A vehicle employs coolant, which is generally made of 50% water and 50% anti-freeze. The coolant cools down the engine of your car, particularly during scorching summer days. However, during the winter season when you want warm air, the coolant in your car comes to the heater core from the car engine. The heater core blows out heat in your car.

The heater core blows out cool air for a few minutes in the beginning since the car engine takes time to heat up so that it can heat up the coolant and thus warm up the car’s interior. However, if cool air blows out even after a few minutes, then you should check the coolant level in your car’s engine.

Insufficient coolant will not be able to pass through the heater core and thus will not create heat in your car’s interior. Additionally, an inadequate amount of coolant will not even cool your car. If you are facing any issues with the cooling system of your car, then you can vacuum the AC system in your car.

2. Issues with the Heater Core

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The heater core of your car can also have some problems, such as:

  • The coolant might not properly pass through the heater core
  • The air coming out of the blower motor is not guided through the right path
  • Clogged tubing of the heater core

If your car has enough coolant level and still it is blowing out cool air, then you need to inspect its heater core. In case, you think that your vehicle’s heater core has gone awry, then you need to look for some cues, including a sweet-smelling, fruity stench, fog inside the car, overheating of your car’s engine, or your coolant finishing up very rapidly.

3. Broken or Blocked Heater Buttons

The heater controls of your car can stop working after they have been used for many years. If you have a sufficient amount of coolant level in your car and the heater core is also working properly, then you need to check your heater controls as well as the heater control valve.

You might have to replace them if they have gone amiss. The heater control valve is situated under your car’s hood and is used to turn on or turn off the heat.

4. Stuck Thermostat

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Your car thermostat might be dysfunctional in case you see that its gauge is stuck on ‘C’ even after the engine has heated up. A faulty thermostat cannot warn the car that its engine has heated up owing to which the coolant will not be transferred, heat up the heater core, and thus it will blow out cool air.

In such a case, you can fix your car thermostat, which is very economical and easy to do. You can install a new thermostat in your car so that your car heater can work again immediately.


So, these are the reasons as to why your car heater might be blowing out cool air. You can check whether or not your car is facing any of these issues and then fix them accordingly. Your car heater will blow warm air in no time when you take help from the above-mentioned points.

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