What to Do When Car Windows Fog Up?

[MacHailey]

Press the defogger button, turn on the air conditioning (A/C) switch, set the temperature to the lowest, and turn on the external circulation to defog. You can use either cold or warm air 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 is important to note that warm air should not be used for defogging on rainy days, as it may initially worsen the fog. When car windows fog up, always use the external circulation. The reasons for car windows fogging up: 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 of the lower-temperature side 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 promptly, the exhaled air has high humidity, and the windshield will quickly fog up. At this point, you can turn on the air conditioning to blow cold air onto the windshield, using the dehumidifying function to remove the fog quickly. If the humidity is too high and the air conditioning is not effective enough, you can slightly open the windows to quickly reduce the humidity inside the cabin. Of course, combining both methods will yield faster results. Air Conditioning Warm Air: Use the method of reducing the temperature difference to remove fog. In winter, use warm air to blow hot air onto the glass, quickly raising the temperature of the front glass and reducing the temperature difference between the inside and outside surfaces of the window. This can prevent excessive fogging on the windshield. However, it should be noted that the rear and side windows heat up more slowly, so it takes longer to remove all 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 frost to form on the outside of the windshield over time. Spraying Anti-Fog Agents for Prevention: Spray a small amount of defogging agent onto the car windows and wipe it clean to remove dirt and stains. While polishing the glass, a thin transparent protective film is formed on the glass, effectively preventing water vapor from condensing and forming fog. This is especially suitable for cold winters. Alternatives to anti-fog agents include dish soap, soapy water, glycerin, alcohol, or salt water. 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, you can open the windows on both sides to create airflow between the inside and outside of the car, reducing the temperature difference and allowing the fog to disappear slowly. The principle of this method is the same as using cold air from the air conditioning. The downside of opening windows for airflow is very obvious—it cannot be used during rain, snow, on highways, or when the fog is heavy. Rear Windshield Heating: Most cars have a rear windshield electric heating function, although the button positions may vary, the function is the same. Turn on the windshield heating switch, and the fog on the rear windshield will disappear in about a minute.