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 remove fog from the 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 defogging. The method of using warm air to defog is the same as using cold air, but 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 car windows. The reason 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 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 promptly, the high humidity of exhaled air can quickly cause the windshield to fog up. At this point, 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 rapidly reduce the humidity inside the car. Combining this with the air conditioning can speed up the process. Air Conditioning Heating: Use the method of reducing the temperature difference to remove fog. In winter, blow warm air onto the glass to quickly raise the temperature of the windshield and reduce the temperature difference between the inside and outside surfaces of the window, preventing heavy fogging. However, note 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 can cause frost to form on the outside of the windshield over time. Applying Anti-Fog Spray or Other Preventive Measures: 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 into fog, 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, you can open the windows on both sides to 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 of opening windows 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 heating function, though the button location may vary. Turn on the rear window heating switch, and the fog will disappear in about a minute.
