How to Deal with Foggy Car Windshield?

[McLillian]

Press the defogging button, turn on the air conditioning cooling (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 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 the purpose of defogging. The method of using warm air to defog is the same as using cold air, but it should be noted that warm air should not be used for defogging on rainy days, as it will initially increase the fog. When the car windows fog up, turn on the external circulation. 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 of the side 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 dehumidification 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 in time, the humidity of the exhaled air is high, and the windshield will quickly fog up. At this time, you can turn on the air conditioning to blow cold air onto the windshield, using the air conditioning's dehumidification function to remove the fog on the windshield quickly. However, if the humidity is too high and the air conditioning is not effective, you can slightly open the windows to quickly reduce the humidity inside the cabin. Of course, you can also use it in combination with the air conditioning for faster results. Air Conditioning Warm Air: Use the method of reducing the temperature difference to remove fog. In winter, use warm air to blow hot air onto the glass, quickly raising the temperature of the windshield and reducing the temperature difference between the inside and outside surfaces of the glass, which can prevent excessive fogging of the windshield in time. However, it should be noted that the rear and side windows heat up 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, otherwise, the outer surface of the windshield may fog up after prolonged use. Spraying 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 from the windows. While polishing the glass, a thin transparent protective film is formed on the glass, which effectively prevents water vapor from condensing on the glass and forming fog, especially suitable for cold winters. Alternatives to anti-fog agents include dishwashing liquid, soapy water, glycerin, alcohol, or salt water. After drying, wipe off excess fibers with chamois or a soft dry cloth, which can ensure the car windows do not fog up for several days. Opening Windows for Airflow: If the fog inside the car is not 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 gradually disappear. The principle of this method is the same as using cold air from the air conditioning. The downside of opening windows for airflow is very obvious: it cannot be used in rain, snow, highways, or when the fog is heavy. Rear Windshield Heating: Most cars have a rear windshield electric heating function, although the button positions 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.

[KiaraFitz]

When the front windshield fogs up while driving, first turn on the air conditioner to blow on the windshield. If the car has a defog button, simply press it; if not, manually adjust the air conditioner to the windshield position. Temperature settings depend on the weather: use warm air on cold days but more slowly, and cold air on hot days or when in a hurry for faster dehumidification. Also, turn on the external air circulation to bring in fresh air—avoid using internal circulation as it can worsen fogging. Slightly opening the windows can also help with air circulation. After parking, you can safely wipe the glass clean, but don’t do this while driving as it’s dangerous. Prevention is key: avoid leaving wet items like umbrellas or hot drinks in the car to keep the interior dry. Regularly using anti-fog spray or soapy water to clean the glass can reduce the chance of fogging—these small steps can be quite effective.