Auto Air Conditioning Maintenance Tips

By The Mother Earth News Editors
Published on July 1, 1987
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ILLUSTRATION: DON OSBY
An auto air conditioner — as well as its close kin, the home air conditioner and the refrigerator — moves heat. Refrigerant picks heat up inside the car and carries it outside.

Other than a radio, auto air conditioning is the most popular new-car accessory today. Over 75% of all pride and joys roll out of the showroom with “factory air.” What’s more, each year a half-million used cars have air conditioners added.

Auto Air Conditioning Maintenance Tips

Even though air conditioners are only slightly less common than rear-view mirrors, few car owners have any clear idea just how one works or what to do if it doesn’t. It’s an unknown realm where the normally adventurous amateur mechanic fears to tread. There is some reason for this reluctance. Any air-conditioner problem that involves opening the pressurized system to the atmosphere should probably be left to the pros, who have the expensive tools and expertise needed. But a whole host of common problems fall short of drastic measures and are easily within reach of a shade-tree mechanic. And even if you don’t qualify for that title, and decide to leave the work to others, you’ll be better off if you understand the trouble.

How Does Auto Air Conditioning Work?

It’s very simple: An auto air conditioner — as well as its close kin, the home air conditioner and the refrigerator — moves heat. Refrigerant picks heat up inside the car and carries it outside. Technically termed a vapor-compression cooler, an air conditioner relies on two basic physical principles to capture and release heat:

1. When a liquid changes to a gas (boils), heat is absorbed; when the gas condenses, the same amount of heat is released. The amount of heat needed to vaporize a pound of water, to make the leap from 211 degrees Fahrenheit to 212 degrees Fahrenheit, is 970 Btu (British thermal units). By contrast, it takes only 1 Btu to get from 210 degrees Fahrenheit to 211 degrees Fahrenheit. It’s this change of phase that allows an air conditioner to get so much work out of a small amount of refrigerant.

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