Press the defogging button, turn on the air conditioning (A/C) switch, set the temperature to the lowest, and activate the external circulation to defog. Both cold and warm air can be used to defog car windows, but warm air is slower than cold air. The most effective method is using cold air, which blows dry cold air directly onto the glass, preventing water vapor from condensing on the glass 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 can initially worsen the fog. Always use external circulation when defogging car windows. 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 saturation vapor pressure than the surrounding environment, causing water vapor to gather on the glass surface and form tiny 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 can quickly fog up. In this case, turn on the air conditioning to blow cold air onto the windshield, using its dehumidifying function to remove the fog quickly. If the humidity is too high and the air conditioning is not effective, slightly open the windows to rapidly reduce the humidity inside the car. 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 quickly raises the temperature of the 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. Avoid setting 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 Agents for Prevention: Spray a small amount of anti-fog agent onto the car windows and wipe it clean to remove dirt and stains. While polishing the glass, a thin transparent protective film forms on the surface, effectively preventing water vapor from condensing into fog. This is especially useful in 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 any excess 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, 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 is 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. Turning on the windshield heating switch will make the fog on the rear windshield disappear in about a minute.
