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 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 surface and achieving defogging. The method for using warm air to defog 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 fogging. Always use external circulation when defogging the car windshield. The reason for fogging on car windows: There is a temperature difference between the inside and outside of the car. If the temperatures inside and outside 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 droplets, resulting in fogging. 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 high humidity from exhaled breath can quickly cause fogging on the front windshield. In this case, turn on the air conditioning to blow cold air toward the front windshield, using its dehumidifying function to quickly remove the fog. If the humidity is too high and the air conditioning is not effective enough, slightly open a window to rapidly reduce the humidity inside the cabin. Combining this with the air conditioning can yield faster results. Air Conditioning Warm Air: Use warm air to reduce the temperature difference and remove fog. In winter, blowing warm air onto the glass quickly raises the temperature of the front windshield, reducing the temperature difference between the inner and outer surfaces and preventing excessive fogging. However, note that the rear and side windows heat up more slowly, so it takes longer to completely remove the fog. Whether using automatic or manual air conditioning, turning it on helps with dehumidification. Avoid setting the temperature to the coldest position, as prolonged use may cause fogging on the outer surface of the windshield. Applying Anti-Fog Spray: 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 forms, effectively preventing water vapor from condensing and fogging the glass. This 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 can keep the windows fog-free for several days. Opening Windows for Airflow: If the fog inside the car is not too heavy, opening the side windows can create airflow between the inside and outside, reducing the temperature difference and gradually dissipating the fog. The principle is the same as using cold air from the air conditioning. However, this method has obvious drawbacks and cannot be used during rain, snow, on highways, or when the fog is heavy. Rear Windshield Heating: Most cars have a rear windshield heating function, though the button location may vary. Turning on the heating switch will remove fog from the rear windshield in about a minute.
