Press the defog 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 the car windows, but warm air works slower than cold air. The most effective method is using cold air, as it 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 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 the car windows fog up. The reasons 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 accumulate 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 and the air conditioning is not turned on promptly, the high humidity of exhaled air 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 dehumidifying function to remove the fog quickly. If the humidity is too high and the air conditioning is not effective, slightly open a window to 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 glass can quickly raise the temperature of the windshield, reducing the temperature difference between the inside and outside surfaces of the window, thereby preventing excessive fogging. 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. The temperature control should not be set to the coldest position, as this can cause the outer surface of the windshield to fog up over time. Applying Anti-Fog Agents 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 into fog on the glass, which is especially useful in cold winters. Alternatives to anti-fog agents include dishwashing liquid, 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 can 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 dissipate slowly. The principle of this method is the same as using cold air from the air conditioning. However, the downside of opening windows is obvious—it cannot be used in rainy or snowy weather, on highways, or when the fog is heavy. Rear Window Heating: Most cars have a rear window electric heating function, though the button location may vary. The function is the same. Turn on the rear window heating switch, and the fog on the rear window will disappear in about a minute.
