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 the car windshield, 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 of using warm air is the same as using cold air, but it's important to 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 the car windshield. 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, if the air conditioning is not turned on in time, the high humidity from exhaled breath can quickly cause the front windshield to fog up. At this point, turn on the air conditioning to blow cold air onto the front windshield and use the dehumidifying 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 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, blowing warm air onto the glass quickly raises the temperature of the front windshield, reducing the temperature difference between the inside and outside surfaces of the glass, thereby 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 frost to form on the outside of the windshield over time. Applying Anti-Fog Spray 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, 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 dishwashing liquid, soapy water, glycerin, alcohol, or saline solution. After applying, let it dry and then wipe off any excess 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, opening the windows on both sides can 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 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, though the button location 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.
