How To Defog a Windshield


Vehicle windshields can fog up for various reasons depending on humidity and temperature levels on the inside and outside. If the windshield of your car or truck frequently clouds to the point where you cannot see the road or your surroundings, you should try one or more of these defogging methods. Depending on the climate where you live, you may also want to consult with experts at the best auto parts store about defroster or AC system maintenance and repairs, windshield wiper blade replacement or the most effective anti-fog treatment.

Defogging the Inside

When it’s cold and dry outside, fog tends to form on the interior of windshield glass. Try to avoid wiping away buildup with your hand, as this can smudge the glass. Instead, run the defrost vent without heat or open the windows to rapidly drop the temperature and adjust the moisture level. Equalizing humidity levels and temperatures is the best solution when the windshield has become fogged while you are on the road and you need to restore visibility as quickly as possible. Depending on the weather, this defogging method might make conditions in the interior cabin less comfortable.

It is also possible to evaporate moisture by running the heater through the defrost vent. Auto glass specialists recommend maintaining similar exterior and interior moisture levels by allowing the heater to bring in outside air rather than recirculating moist cabin air. These methods are most effective for fog that forms on the inside of a windshield or rear-view window. Make sure that the windshield and windows are as clean as possible by applying specialized car interior cleaning products formulated for glass. You can also apply interior windshield glass treatments formulated to prevent fog buildup. The best auto parts store will have a variety of products that can help to resolve the issue if the defroster in your car or truck fails to quickly clear fog.

Defogging the Outside

Fog can also form on the exterior of windshield glass in very humid weather conditions. In this situation, it is dryer and may even be cooler inside a vehicle than it is outside. If the temperature is mild, you might try running the heat on low to warm the inside of the windshield and limit the amount of moisture that condenses on the exterior side. If it’s too hot to run the heater, see if you can at least turn the air conditioning down or off. If the heat is too extreme, try using the windshield wipers on your car or truck to wipe away the buildup of fog and condensed moisture. Once again, it is important to make sure that the exterior surface of your windshield glass is clean. A combination of dirt, road debris and fog can significantly impair your ability to see the road and your surroundings. Windshield wipers may also leave smears on dirty glass that scatter light or obstruct the view. The best car washing products can make it more difficult for spots to stick to your windshield and may prolong the life of wiper blades.