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What’s Up With That? The Cool Science Of Air Conditioning

A look at what goes on behind the vents

Old North State summers get so daggum hot that you could slow-cook a chuck roast on your dashboard. When the outside air temperature is in the 80 to 100 degree range, the inside temperature of a car parked in direct sunlight can shoot up to about 150 – more than enough to braise a slab of beef. So if you feel like you’re roasting when you’re riding in a car without air conditioning, well, you are.

If you’re into that sort of thing, the cult classic cookbook, “Manifold Destiny” will tell you pretty much everything you’ll want to know about the automobile as a culinary device. For those of us who would rather not use our car as an oven, though, its air conditioning (A/C) system was designed solely to keep us comfortable as we’re cruising down those sun-strewn summer highways. 

And it works so well, it’s easy to take it for granted. Until it doesn’t work so well. Let’s hope that’s not after your car has been sitting in the middle of a North Carolina parking lot on a summer afternoon. 

Actually, you don’t have to hope, because your A/C gives you some clues that it needs a little attention well before it breathes its last cool breath. Even better news is that, if you’re the cautious type, you don’t even have to wait for those clues. When the weather starts turning warm, a little maintenance checkup can sometimes save you from sweating over a hot commute and the cost of a big repair. 

Let’s take a quick look at that little comfort machine, so you can recognize the signs that may be about to give out. 

A/C: The Basics

There are six main components of your A/C system: a compressor, a condenser, a thermal expansion valve, an evaporator, an accumulator, and a chemical refrigerant. Each component has to work properly for you to get the relief you want. If one piece underperforms or fails, your body’s cooling system takes over. In other words, you’re sweating like crazy.

Here’s how it works: 

The compressor compresses the refrigerant from a gas into a liquid and sends it down the refrigerant line to the condenser. 

Inside the condenser, the refrigerant flows through a small grid. Air passes across this grid, removing heat from the refrigerant, which then passes over to the expansion valve.

At the expansion valve the pressure in the line is reduced, and the refrigerant turns back into a gas. This gas goes into the accumulator. 

The accumulator removes moisture from the refrigerant, and sends its drier, cooler product to the evaporator. 

Air from outside blows across the evaporator core, giving its heat to the refrigerant, and becoming cool in exchange. Since cooler air holds less moisture, it also becomes less humid (that’s why you see puddles of water under recently parked cars on hot summer days; just a few minutes ago, that water was making the air sticky). 

Finally, that delightfully cool, dry air passes through your cabin air filter and reaches you as a fresh, cool breeze (or a nice cold blast, if you’re in the mood).

Noticing There’s an A/C Problem

There are two main clues that will let you know your A/C system has a problem: smell and noise. If it exudes a damp or musty stench, that’s your first clue. Typically, this smell means that microorganisms like mold, mildew, or fungi have taken up residence in your system. Why did they start to grow there? They like moist surfaces. So, the smell is a sign that your A/C is not cooling the air enough to reduce its humidity to the desired level. 

Maybe the air smells fine, but you hear a noise coming out of your vents. That’s clue number two. A buzzing sound is usually the result of too much refrigerant passing into the compressor, which could leak and cause damage to your car.

Maintenance Beats Repair

Bad smells and buzzing usually mean trouble, but you don’t have to wait for trouble. To keep everything cool, just ask us to give your A/C a quick check-up when the weather starts to turn warm. You’ll not only avoid unpleasant smells, irritating noises, and unwelcome roasting, you can avoid the larger repair – or replacement – that can follow those signs of trouble. Or, if you’re into that sort of thing, you could just pick up a copy of “Manifold Destiny,” and explore your talents as a “chef de cruise-ine.”

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