How to Stop a Windshield From Fogging Up

by Brittany Tucker
Hemera Technologies/ Images

Driving with a foggy window can be irritating, not to mention dangerous. According to the UIUC Department of Physics, car windows fog up when water condenses on them, occurring on the inside and outside of the window. Learning how to properly prevent your windshield from becoming foggy is a must if you want it to stop fogging up.

Step 1

Ammonia-based window cleaner

Rub the inside of the windshield down with an ammonia-based window cleaner. The DeAnza College recommends cleaning the inside of the window with an ammonia-based window cleaner to remove the buildup of film that commonly emanates on windshields. Rub the solution on the windshield with orderly horizontal or vertical strokes. Reapply regularly for maximum results.

Step 2

Use your defogger/defroster setting regularly

Use your vehicle’s defogger/defroster heat setting regularly. According to the Alaska Department of Public Safety, you can prevent fogging while warming up your car by turning on the heater and the defroster.

Step 3

Select the fresh air setting

Check that your air conditioner or heater is on the fresh air setting instead of the recirculate setting. According to DeAnza College, the recirculate setting reuses the humid or moist air already in the car.

Crack your window open

Crack your window open. According to, you can leave your window cracked open a little bit to keep your windshield from fogging up.

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