Getting the most from your car’s A/C

edmunds ac

edmunds.com

via How to get the most out of your vehicle’s AC, clarionledger.com

PDF: ACTips1ACTips2

If you’re of a certain age, you probably remember the old “4/40” system for keeping cool while driving in the summer months. Driving around at around 40 miles per hour with all four windows down got the air moving in the torrid heat of a Southern summer, and provided a welcome escape for generations of Mississippians.

While most of us consider air conditioning to be a necessity in our vehicles, it wasn’t always so. Early automobiles were uncooled, even as the new air-conditioning systems (if you could afford them) made homes and businesses feel like a crisp March morning even in the dog days of August. In 1933, Popular Science reported that a New York company had installed an air conditioning unit in a commercially available vehicle for the first time.

Although not commercially successful at first because of the unwieldy equipment required, cost and danger of carbon monoxide poisoning, the idea took off, and the technology made steady improvements. In the years after, Packard and Cadillac experimented with various technologies. But in 1953, the new Chrysler Imperial featured an optional air conditioning that would be recognizable as a modern system.

Since then, many more innovations have made air conditioning a staple on most vehicles. But many drivers still are probably not getting the most effective use of it. Recently, Consumer Reports’ Patrick Olsen wrote a great column with five tips:

Don’t pre-cool. Olsen explains that your car’s air conditioning works much better when you’re actually driving, because the faster the engine turns, the faster the compressor runs, which lets the system cool more effectively. Don’t waste time and gas by letting your car run before you go.

“If the interior is really hot, crank up the fan when you start driving, and open just the rear windows for 10 to 20 seconds,” Olsen advises. “This forces all the hot air out of the cabin. Don’t open the front windows — that only moves the heat out of the front of the car, and it will leave the air in the back of the cabin hot and stagnant.”

Go low. Since most vehicle air-conditioning systems cool the air to about 38 degrees, if you set the temperature higher, you can be making the system work harder since it must re-heat the air. Olsen advises setting the temp to the lowest setting, then using the fans to adjust the temperature.

Don’t recirculate. Most cars have a “recirculate” button, which takes air from the front of the cabin and pulls it back through the system. But while using this feature might make the driver and front-seat passengers comfortable, it can make rear-seat passengers hotter.

Turn off stop/start mode. Some newer vehicles have a system that stops the engine when idling, to cut down on fuel use and emissions. Olsen suggests turning it off, because it can make the compressor stop running, making your car hotter when stopped or in stop-and-go traffic.

Clean the filter. A dirty cabin air filter (just like the one in your house) can reduce the efficiency of your system and make it work harder. If your filter is easily accessible, clean it often.

And as for the age-old debate about whether using the air conditioner uses more gas than riding with the windows open, most expert sites I consulted noted, “it depends.”

Conventional wisdom says the air conditioner uses more gas, and that’s usually true. Car and Driver did a study in 2008 in which they tested this theory and recommended turning the air conditioner off and opening the windows (at lower speeds) to save a few miles per gallon. But at higher speeds, the engine is running faster, making the air-conditioning system use less fuel. Automotive site Edmunds.com notes, “in our experience, it’s not worth the argument because you won’t save a lot of gas either way. So just do what’s comfortable.”

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