Car heater tips: Windows fogging up? Turn on the air conditioner

WASHINGTON — Getting the most out of your car’s heater might involve counterintuitive practices, such as turning on the air conditioner to prevent foggy windows from limiting visibility.

“Keep the AC on, because it’s going to take the condensation out of the air,” Consumer Reports deputy auto editor John Linkov said. “You won’t have to keep wiping the windshield and your side windows with your mittens, or your gloves, or the sleeve of your jacket.”

Also, don’t recirculate. Air recirculated through the cabin likely holds more moisture than fresh air coming in from the outside because people exhale water vapor, Linkov said.

To help clear the air when there are lots of passengers in the vehicle exhaling water vapor, Linkov suggests cracking open a window.

Here are a few other tips from Consumer Reports related to your car’s heater:

Blowing air on “high” through vents faster will not warm it more quickly

“The engine is what generates the heat,” Linkov said. “As soon as you get moving, that’s the key thing.”

Don’t waste time by thinking your car needs to warm up

Turn the key on most modern, conventional gas and diesel cars and you can safely drive away in five or six seconds — even in extreme cold.

“If you have a heavy duty truck, you’re definitely going to have a different set up with diesel fuel,” Linkov said. “You’re going to want to keep the vehicle running so that if it’s in extreme, extreme cold, you don’t have any problems with fuel ‘sludging’ up.”

Don’t forget your friends in the back

To help heat get beyond the front seats: adjust air flow toward your feet where it can push back underneath seats. Also, tilt top vents toward the ceiling so warm air can flow toward the rear.

Feel free to get toasty

Unlike your car’s air conditioner that uses a separate compressor, heat that circulates through the cabin comes from the car’s engine. So, Linkov said, use the heat as much as you want.

“If you’re not using it, it’s getting dumped back into the system, into the radiator,” Linkov said. “You’re not going to hurt your fuel economy, you’re not going to hurt your gas mileage; it’s not costing you any extra money.”

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