How to Deal with Foggy Windows When Using Air Conditioning in Winter?
4 Answers
Press the defogging button, turn on the air conditioning cooling (A/C) switch, set the temperature to the lowest, and use the external circulation to remove fog. 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 the purpose of defogging. The method of using warm air to defog is the same as using cold air, but it should be noted that warm air should not be used for defogging on rainy days as it may initially worsen the fog. When car windows fog up, use the external circulation. The reason for foggy car windows: 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 cooling and dehumidifying 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 in time, the high humidity of exhaled air can quickly cause the windshield to fog up. At this point, turn on the air conditioning to blow cold air onto the windshield, using the dehumidifying function to quickly remove the fog. If the humidity is too high and the air conditioning is not effective, slightly open a window to rapidly reduce the humidity inside the car. Combining this with the air conditioning will yield faster results. Air Conditioning Warm Air: Use the method of reducing the temperature difference to remove fog. In winter, blow warm air onto the glass to quickly raise the temperature of the windshield and reduce the temperature difference between the inner and outer surfaces of the glass, preventing excessive fogging. However, it should be noted that the rear and side windows heat up more slowly, so it takes longer to completely remove the fog. Whether the air conditioning is automatic or manual, turning it on helps with dehumidification. Do not set the air conditioning temperature to the coldest position, as this may cause the outer surface of the windshield to fog up over time. Applying Anti-Fog Spray for Prevention: Spray a small amount of defogging agent on the car windows and wipe it clean to remove dirt and stains. While polishing the glass, a thin transparent protective film is formed, effectively preventing water vapor from condensing on the glass and forming fog, which is especially useful in cold winters. Alternatives to anti-fog spray include dish soap, soapy water, glycerin, alcohol, or saline solution. After applying, let it dry and then wipe off excess residue with a chamois or soft dry cloth. This will keep the car windows fog-free for several days. Opening Windows for Airflow: If the fog inside the car is not too heavy, open the windows on both sides to create airflow between the inside and outside of the car, reducing the temperature difference and gradually dissipating the fog. The principle of this method is the same as using cold air from the air conditioning. However, the downside of opening windows is very obvious: it cannot be used during rain, snow, on highways, or when the fog is heavy. Rear Window Heating: Most cars have a rear window heating function, though the button location may vary. Turn on the rear window heating switch, and the fog on the rear window will disappear in about a minute.
I've been driving for decades, and foggy windows in winter are a common issue that needs proper handling. After getting in the car, start the engine first, turn on the A/C switch, set the fan to high and direct it at the windshield to quickly remove moisture and fog. If the fog is heavy, switch to external circulation mode to let dry outside air help dehumidify. When washing the car, remember to clean the inside of the glass thoroughly, as oil stains can worsen fogging. Keep a bottle of defogging spray handy for good preventive effects. If fog reappears while driving, don't hesitate to pull over and deal with it—safety comes first. Blurry vision is too dangerous; don't let small issues lead to major accidents. Regular vehicle maintenance is also crucial; replace dirty filters to prevent the A/C from underperforming.
As a commuter who drives to work every day, I pay special attention to visibility safety during winter driving. After getting in the car, I immediately turn on the defogging function of the air conditioner by pressing the auto button or manually adjusting the airflow mode to the windshield, setting the fan speed to medium or high for effective defogging. Meanwhile, I set the temperature to a comfortably warm level, avoiding excessive temperature differences. Using the external air circulation is a must, as it quickly draws in cold air for dehumidification. Before getting in the car, I make sure to clean the snow off my shoes to reduce interior moisture; I also regularly clean the air filter to prevent clogging and maintain dehumidification efficiency. If fog suddenly appears while driving, I pull over safely before adjusting settings to avoid distracted driving. By adopting these simple habits, I’ve never been delayed by fogging issues on my way to work—driving safety is always the top priority.
I have some technical knowledge about cars. Fogging in winter is mainly caused by condensation due to temperature and humidity differences. When starting the car, turn on the A/C and select the defrost vent to blow directly onto the windshield to remove moisture. Using the external air circulation is essential as it helps bring in dry air and improves efficiency. Don’t forget to check if the air conditioning system is functioning properly, and replace the filter if it’s dirty. For short trips, don’t rush to turn off the A/C—maintain a moderate airflow to completely clear the fog. From a safety perspective, wait until the fog has fully dissipated before driving, as poor visibility is a major hazard on the road.
