Which Button to Press When the Car's Windshield Fogs Up?
2 Answers
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 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 for defogging with warm air is the same as with 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, external circulation should be activated. 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 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 and the air conditioning is not turned on in time, the exhaled air has high humidity, quickly causing the windshield to fog up. At this time, turn on the air conditioning to blow cold air onto the windshield, using the dehumidifying function to quickly remove the fog. However, if the humidity is too high and the air conditioning is not effective enough, slightly open a window to quickly reduce the humidity inside the car. Of course, combining this with the air conditioning will yield 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 window. This can prevent excessive fogging on the windshield, but 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. The temperature control should not be set to the coldest position, as prolonged defrosting can cause the outer surface of the windshield to fog up. Applying Anti-Fog Spray 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 on the glass and forming fog. This is especially suitable for cold winters. Alternatives to anti-fog spray include dishwashing liquid, soapy water, glycerin, alcohol, or salt water. After drying, wipe off any excess fibers with chamois or a soft dry cloth, which can keep the car windows fog-free for several days. Opening Windows for Airflow: If the fog inside the car is not heavy, open the side windows to 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. The downside of opening windows is very 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 heating function, although 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.
Encountering foggy windshields is an old acquaintance for drivers, especially on rainy days or in winter. My advice is not to rush onto the road immediately. Look for the button with a fan-shaped wavy line icon on your dashboard or air conditioning control panel—pressing it activates the defogging mode. The system automatically blows warm or cold air onto the glass to speed up moisture evaporation. Meanwhile, slightly opening the windows to ventilate and reduce humidity can prevent fog from quickly returning. The main cause of fogging is the temperature difference between the inside and outside of the car, leading to moisture condensation. Therefore, regularly wiping the inner side of the glass with anti-fog spray or using the air conditioning's external circulation can reduce the frequency of occurrence. With over a decade of driving experience, I find this method both worry-free and safe.
