How your car’s air conditioning system works – how to troubleshoot
How Your Car's A/C System Works
Have you ever wondered how your car's air conditioning system works? How it seems to magically create cold air on a hot day? Here are the basics of how your car's air conditioning works.
A gas such as Freon or another refrigerant is placed in a sealed system. The gas actually doesn't add cold air, rather it removes heat from it's environment.
A compressor - the main component of your car's A/C system - takes and pressurizes this refrigerant gas. The gas absorbs heat around it and this hot, compressed gas goes through a condenser where it is cooled. A condenser is essentially a small radiator that you will find mounted in front of your car's big engine radiator. This cooled gas then turns into a liquid. This very cold, high pressure liquid is then circulated through an evaporator. An evaporator is also a small radiator that is usually located under the dashboard of your car. When a fan forces air across the evaporator, the air is cooled much like air would be cooled if you blew air across a pile of ice cubes. In reality, the refrigerant in the evaporator absorbs heat from the stream of air forced across it, and hence the air temperature is reduced and it feels like cold air has been created.
This cold air is what you feel inside your car.
Meanwhile as the A/C system keeps working the liquid refrigerant warms up and turns into gas again and returns to the compressor to repeat the cycle.
Your car's air conditioning system is also equipped with a control valve that allows you to control the temperature of the air that reaches you. You also control where you want the air directed in your car to your face, your feet, or the windshield.
That is the very basic explanation of how the A/C works. There is a lot more that could be added from physics standpoint and otherwise. We are typically happy as long as there is cold air coming out and the A/C is working.
So, what typically goes wrong if your car's A/C system seems to stop working? It will usually be one of three things:
1.) The refrigerant has slowly leaked out over time and it needs recharging. This is something you can have your local auto repair shop fix for you.
2.) Your car's interior fan has failed. If your fan is not working, the motor may have failed or you may have simply blown a fuse.
3.) Your car's temperature control valve(s) are not functioning properly. For example, it might be possible that your A/C system is working just fine, but the valve that controls the heat is stuck open and continues to pour heat into the car in spite of the A/C system's operation. This can be a little tricky to fix yourself, but for many cars, it is an inexpensive fix by your local repair shop.
4.) The compressor has failed or the belt or belt clutch that operates the compressor has failed. Look under the hood to be sure all your belts appear to be in place. If you hear a loud squeal from under the hood when you turn on the A/C system that may be a sign that the belt is loose, or the compressor is failing or has failed. If the compressor is failing, it is important to have the compressor replaced before it fails to prevent further damage to the A/C system or your engine's belts.
Note. Freon is no longer used as the refrigerant gas in modern vehicles because it suspected to damage the earth's ozone layer.
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