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How to Use Car Air Conditioning, Rain or Shine

Climate Control and Car Air Conditioning: Comfort and Safety!

In 1886, the world’s first automobile was invented, and it didn’t come with much more than three wheels and a single-speed transmission. It’s been over a century, and now you have lots of goodies: four wheels, doors and 10-speed transmissions, for example. Car air conditioning has been a feature in most automobiles for over 50 years, and yet there are millions of people who still don’t fully understand how it works.

How Car Air Conditioning WorksFoggy windows are par for the course when it rains with the AC still on.

Almost every vehicle today comes with air conditioning standard, except for the base Jeep Wrangler, for example. You may think you know how to use air conditioning, but it’s slightly more complicated than selecting “Cold” on the climate controls. First, what does car air conditioning actually do? When you find out the air conditioner is really a heat pump, then the obvious question is, “How and why does it pump heat?”

The air conditioning system has three main components to be aware of. The compressor is located in the engine compartment, the evaporator is located in the climate control system air box, and the condenser is located in front of the radiator. The compressor circulates refrigerant, usually R-134a, through the condenser and evaporator, which are connected via tubes and hoses. The climate control fan blows air over the evaporator, and any heat in the air is absorbed by the refrigerant.

Cold air comes out the other side of the evaporator and through the vents into your car, while warm refrigerant circulates to the condenser. Another fan blows air over the condenser, and heat in the refrigerant is released to the air outside the vehicle. Finally, the refrigerant circulates back to the evaporator to collect more heat.

Granted, an oversimplification, but that’s essentially what car air conditioning does, which is why the inside of the car gets cooler when you turn on the air conditioner.

How to Use Car Air Conditioning — Even if It’s Cold

Most automakers put air conditioning to good use in this manner, which is why turning on the windshield defroster may automatically turn on the air conditioning. Resist informing your service writer that the car is defective because it engages the air conditioner “on its own,” it was actually designed that way.

Some drivers instinctively reach to turn off the air conditioner, thinking “air conditioner = cold air,” which is only half the story. Really, you should think “air conditioner = dry air.”

Because cold air cannot hold as much moisture, any humidity in the air condenses in the evaporator when the air conditioner is operating. That’s why a puddle of water collects under your car when you’re using the air conditioning on a humid day.

In the modern automobile, the evaporator is located before the heater core in the air box. This means that temperature is controlled independently of the air conditioner. When you turn on the air conditioning, cold and dry air comes from the evaporator. After going through the heater core, the result is hot and dry air.

Hot and dry air blowing on your windshield is far more effective at defogging than hot humid air, so ignore that urge to turn off the air conditioner on a cold or rainy day. This will improve your visibility, and you won’t have to resort to a rag to defog your windshield, which keeps your hands on the steering wheel and makes you a safer driver.

Check out all the air conditioning system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on car air conditioning, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Pixabay


Benjamin Jerew View All

Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.

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