Car AC Not Blowing Cold Air? Common Causes (& How to Fix)

Driving a car without AC on a hot summer day is awful. But what can cause an AC not to blow cold air? Let's find out!

Car Ac Not Blowing Cold Air

Imagine driving peacefully on a bright sunny morning, listening to your favorite music, and enjoying the scenery around you.

Now, imagine that your car’s air conditioning system suddenly stops blowing cold air; how would you feel?

Absolutely desperate, of course! Any problem in your car that has to do with air conditioning can be very distressing, especially if you live in a hot country. Let’s take a quick look at the possible reasons:

The most common reason why an AC is not blowing cold air is due to an empty AC system, caused by a leak. It can also be caused by a faulty AC pressure switch, a bad compressor, or a damaged AC condenser. In more rare cases, it can also be an issue with your heat controller.

The main issues that occur with the car’s air conditioning system are due to poor maintenance. Here is a more detailed list of the most common causes of a car AC not blowing cold air.

9 Causes of Car AC is Not Blowing Cold Air

1. Empty AC System

Ac System Refill

Your AC system is filled with an ac refrigerant, making sure the whole system is working correctly. This refrigerant system is of high pressure, and it can reach 15 bars when the car is running.

For the AC system to work properly, it needs this pressure and a specific amount of refrigerant.

If you leak in the AC system, the pressure will get lower and lower and finally stops working at all.

The AC system is also leaking very slowly through hoses and other places. This is very slow, though, and you can expect to refill it every 6-7 years.

If you haven’t refilled it in 6-7 years, it is definitely time for a refill, and if it was more recently you filled it, it is time to check for any leaks.

Only let a certified workshop with the proper equipment do work to your AC system. The AC system should always be leak checked before a refill.

RELATED: Does AC Leak Sealer Work?

2. Faulty AC Pressure Switch

Ac High Pressure Switch

There are two AC pressure switches in your car that monitor the high-pressure side and the low-pressure side of the air condition system for safety reasons.

If the pressure gets too high – it will stop the AC compressor from cooling the system anymore because of safety reasons.

If the pressure gets too low, it will also shut off the function of the AC compressor.

If this AC pressure is faulty, it can give the AC compressor faulty signals to stop – even if it shouldn’t, and this will cause your AC system not to function at all.

3. Faulty AC Compressor Clutch

Replace Ac Compressor Clutch

Some car compressors use a clutch inside the air compressor. The serpentine belt powers the air compressor pulley, and when you activate the AC – the clutch is connecting the air compressor to the pulley. This makes the AC compressor to spin and power the AC system.

If this clutch is too worn, it may cause the AC compressor not to start at all. You can replace this clutch in many AC compressors or even remove shims for the clutch for it to work a little bit more.

Most newer cars have a variable AC compressor, though, and in this case, no AC compressor clutch can fail.

RELATED: How Much Does an AC Recharge Cost?

4. Faulty AC Compressor

Ac Compressor

There could not only be damages to the AC compressor clutch; the compressor itself can also fail if you are unlucky. The AC compressor pumps refrigerant around in the AC system for it to cool properly. It happens that the pump fails and stops pumping at all, and this will cause your AC system to blow hot air.

If the AC compressor fails, you often have to flush the whole AC system afterward because there might be metal pieces everywhere.

5. Damaged AC Condenser

Ac Condenser

The condenser is installed in the front of the car, transferring heat away from the evaporator inside the car. The AC condenser is often installed in front of the radiator, and this makes it sitting in a very exposed position for stones and other parts that can damage it at high speeds.

This often causes the AC condenser to start leaking refrigerant, which will cause the AC refrigerant to pour out. You do often have to replace the AC condenser at least every 10 years.

6. Damaged Condenser Fan

Ac Condenser Fan

The condenser needs wind through it to remove the heat properly. As you might understand, it won’t pass any wind through it at lower speeds. For this, we need a fan that can run instead of the wind at lower speeds.

If this fan fails, there might be a problem with the AC system at lower speeds. If you notice that your AC is working at higher speeds but not lower, there could definitely be a problem with the condenser fan.

7. Clogged Cabin Filter

Cabin Air Filter

A cabin air filter is responsible for filtering the air that enters the vehicle’s air conditioning system. The filter catches all the dust and impurities that enter the passenger compartment and can, therefore, become clogged over time.

Also, a clogged cabin air filter leads to a deterioration in the air conditioning system’s cooling. It is recommended to check and clean the cabin air filter frequently. If you want to know more, you can read our article Why should I replace my Cabin Air filter.

If you feel that there is a meager amount of air blowing through the vents, it could absolutely be a clogged air filter.

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8. Faulty Blend Door Actuator

Blend Door Actuator

When you turn the heat controller on the AC control unit, there needs to be something that controls the heat inside the car. This part is called the blend door actuator inside your car, and it is controlling a flap that is redirecting hot or cold air inside of your car.

This setup can look a little bit different, but the main function is the same. If this actuator is faulty, your car might blow hot air out from the vents even if you require cold air.

9. Faulty Heat Controller / Air Condition Control Unit

Car Air Climate Controls

The last cause on this list is a faulty heat controller. If this fails, it may send the wrong signal to the blend door actuator, and this may cause it to blow hot air instead of cold.

Most older cars have wires for this, but newer cars have an electronic signal between these, which can fail. The Air condition control unit is often quite expensive, and it is recommended to check the other things first.

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.