Press the defogging button, turn on the air conditioning (A/C) switch, set the temperature to the lowest, and turn on the external circulation to remove fog. Both cold and warm air can be used to defog car windows, but warm air works slower than cold air. The most effective method is using 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 using warm air is the same as cold air, but note that warm air should not be used on rainy days as it may initially worsen the fog. Always use external circulation when defogging car windows. The reasons for fogging on car windows: There is a 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 in the form of tiny droplets, forming 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, if the air conditioning is not turned on promptly, the exhaled air with high humidity can quickly cause the windshield to fog up. In this case, turn on the air conditioning and blow cold air onto the windshield. The dehumidifying function of the air conditioning can quickly remove fog. However, if the humidity is too high and the air conditioning is not effective enough, slightly opening the window can quickly 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 windshield can quickly raise its temperature and reduce the temperature difference between the inside and outside surfaces of the window, preventing excessive fogging. Note that the rear and side windows heat up more slowly, so it takes longer to remove fog completely. Whether the air conditioning is automatic or manual, turning it on helps with dehumidification. Avoid setting the temperature to the coldest position, as this can cause frost to form on the outer surface of the windshield over time. Applying Anti-Fog Agents for Prevention: Spray a small amount of anti-fog agent on the car windows and wipe it clean to remove dirt and stains. While polishing the glass, a thin transparent protective film forms, effectively preventing water vapor from condensing and forming fog, especially in cold winters. Alternatives to anti-fog agents include dish soap, soapy water, glycerin, alcohol, or saltwater. After applying, let it dry and then wipe off excess residue with chamois or a soft dry cloth. This can keep the windows fog-free for several days. Opening Windows for Airflow: If the fog inside the car is not heavy, opening the side windows can create airflow between the inside and outside of the car, reducing the temperature difference and gradually eliminating the fog. The principle of this method is the same as using cold air from the air conditioning. However, the downside is 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 electric heating function. The button location may vary, but the function is the same. Turn on the rear window heating switch, and the fog will disappear in about a minute. Using External Circulation: On rainy days in spring or autumn, opening the windows may not be suitable, and turning on the air conditioning may feel too cold. In this case, turn on the external circulation and adjust the air vent to blow onto the windshield. This quickly lowers the temperature on the inner side of the windshield, making the fog disappear quickly.
