Car Heater Blowing Cold Air 7 Reasons and How to Fix it

Winter driving can make it very uncomfortable, particularly if your heater is not working.

Nothing is better than a heater in the car to keep you comfortable and warm.

Heating system problems are very common. In this article, we discuss the most common reasons why you don’t have heat in your cabin.

A low coolant level or malfunctioning thermostat are all common reasons why a car heater produces cold air. You can also experience this problem if your heater is clogged or the controls are not working properly.

Below is a list that explains why your heat doesn't work in your vehicle:

Why is my car heater not cooling?

1. Low Coolant Level

A low level of coolant is the main reason your car heat does not work.

It is easy to find the level of coolant. You will need to locate the reservoir of coolant. It is typically a yellow, green, or blue fluid. It will also have the coolant text printed on its cap in most cars. If in doubt, refer to the owner's manual.

A MAX or MIN indicator should be located on the reservoir. If the level is under the MIN sign or you can’t see any coolant there at all it is definitely time to refill it.

Keep in mind that coolant can reach boiling temperature and should not be opened when it is too hot.

If the coolant level has become too low it may actually have caused air bubbles in the coolant systems and you may need to bleed the car’s cooling system after the refill. This is all we'll discuss further below.

Low coolant levels can indicate a coolant leak and should be addressed immediately.

You can find more information at How to Repair a Coolant Leak

2. Thermostats that are not working properly

The thermostat ensures that the car's engine heats quickly, and keeps it warm at a consistent temperature.

If the thermostat fails, it can cause the engine to not reach the working temperature at all, and therefore you will feel that the car’s heating system is blowing warm air but far away from the temperature it was blowing before.

You should be concerned if you notice that the temperature gauge is showing that the temperature is not reaching the desired temperature, either 200 F or 90 F.

Learn more: Signs that your thermostat is not working properly

3. Broken Heater Flaps/Blend Door Actuators

The heating core is controlled by flaps located under the dashboard. There is a high chance that the heater won't work as it was intended if one of these flaps is damaged or the electrical actuators are defective.

If you have a newer car with electric motors for the flaps – you will most likely get an error code on them when you scan the system with a diagnostic computer.

The flaps can be located and checked to see if the heating control moves. If they do not – they are most likely broken. You may have difficulty seeing them in many cars because they are usually hidden below the dashboard.

These actuators can also lose their programming and need to be reset with a scanner.

4. Air in the Cooling Systems

Overheating your engine can be very dangerous.

Coolant systems can be contaminated by air if they have been refilled recently or the coolant level has dropped to a low point. Sometimes, the problem can be due to a leaking or bad head gasket.

Airlocks often get stuck in the heater core inside the car, making the car’s heater blow cold air.

To get rid of air in the cooling system, you have to bleed the car’s cooling system. This can be a difficult process if you don't have the right knowledge. I suggest that you let a professional do it.

If you feel that you are comfortable enough to bleed it, you can follow our guide here: How to Bleed Your Car’s Cooling System

5. Broken Heater Controls

There are a number of controls inside your vehicle that can be used to control heating. While you are sitting inside your car, the temperature can be adjusted and many other settings may also be changed. You may find that the controls have become stuck, or even broken.

The controls can easily be damaged because they are made of inexpensive materials such as plastic. There are many videos online that will show you how heating controls can be repaired.

The wires that ran from the thermostat to the actuator were used in older cars. It was common for the metal parts the wires pulled on to break. Unfortunately, you will often need to replace your heater control unit.

Many newer vehicles use electronic heater control systems. The failure of these heaters is extremely rare, however, it's possible to have the entire unit replaced if necessary.

6. Heating Core Clogged

Your heating core could be clogged or bad if nothing is happening. Your heating system's heart is located in the heating core. If it fails, the entire system can fail.

Sometimes, the heating core can become clogged by rust or other debris in the cooling system. You can flush your heater core and get rid of the problem, while other times you will need to replace the entire heater core.

You can see how to flush the heater's core in this video: How to flush the heater core

Heating cores are expensive components. It is difficult to replace as they are often located under your dashboard. The mechanic would charge you about $600 to $1000, depending on your car’s make and model.

FAQ No Heat In Car