How to Deal with Fogging on Both Sides of Car Windows?
3 Answers
Press the defog button, turn on the air conditioning cooling (A/C) switch, set the temperature to the lowest, and turn on the external circulation to defog. Both cold and warm air can be used to defog car windows, but warm air is slower than cold air. The most effective method is to use cold air, which blows dry cold air directly onto the glass, preventing water vapor from condensing on the glass and achieving defogging. The method for defogging with warm air is the same as with cold air, but note that warm air should not be used for defogging on rainy days as it may initially worsen the fog. Always use external circulation when defogging car windows. The reason for car window fogging: There is a certain temperature difference between the inside and outside of the car. If the temperatures inside and outside the car are different, the surface with the lower temperature will have a lower saturated vapor pressure than the surrounding environment, causing water vapor to gather on the glass surface and form tiny water droplets, resulting in fog. Methods to defog car windows: Air Conditioning Cooling: Use the air conditioning's dehumidification function to reduce air humidity and remove fog. In summer, especially when multiple people enter the car and the air conditioning is not turned on promptly, the high humidity from exhaled breath can quickly cause the windshield to fog up. In this case, turn on the air conditioning to blow cold air onto the windshield, using the dehumidification function to quickly remove the fog. If the humidity is too high and the air conditioning is not effective, slightly open the window to rapidly reduce the humidity inside the cabin. Combining this with the air conditioning can speed up the process. Air Conditioning Warm Air: Use the method of reducing the temperature difference to remove fog. In winter, blowing warm air onto the glass quickly raises the temperature of the windshield, reducing the temperature difference between the inner and outer surfaces of the glass and preventing excessive fogging. However, note that the rear and side windows heat up more slowly, so it takes longer to completely defog them. Whether using automatic or manual air conditioning, turning on the air conditioning helps with dehumidification. Avoid setting the temperature to the coldest position, as prolonged use can cause the outer surface of the windshield to fog up.
Foggy windows are the most annoying issue in cold weather. When I first started driving, I often panicked, but gradually figured out the tricks: First, switch the AC to defog mode—that’s the button with a fan shape and an arrow—and remember to turn on the AC to blow cold air onto the glass. In winter, hot air works better for defogging but takes a bit longer. If you’re in a hurry, just crack open the side windows slightly to allow airflow, and the fog will clear instantly. Keeping a microfiber cloth in the car is super handy—a quick wipe makes the glass crystal clear. The key is to regularly check the cabin air filter; a clogged one increases fogging risks. A dehumidifier box also helps when the car’s humidity is high. Following these methods, I’ve hardly been bothered by foggy windows in recent years.
As an experienced driver, I've summarized several practical methods. Fogging mainly occurs due to temperature differences between the inside and outside of the car causing moisture condensation. The core solutions are two points: reducing humidity and adjusting temperature difference. The first trick is using the AC - in summer, directly blow cold air onto the windshield; in winter, turn on the heater but remember to press the defog button along with external air circulation. The second method is physical defogging - temporarily wipe the inner glass with a clean towel, which works quickly but doesn't solve the root cause. The third approach is prevention - start the AC for dehumidification before driving, avoid placing wet umbrellas in the cabin during rainy days, and regularly replace the AC filter. I always keep defogging spray in my car - applying it to the glass every two weeks can prevent fogging for a month. If the side mirrors fog up, remember to turn on the electric heating function - many people overlook this small button.
