What to Do When the Car's Windshield Fogs Up?
2 Answers
Methods to Defog Car Windows: Press the defog button inside the car. Air Conditioning Cooling: Reduce air humidity to remove fog. Air Conditioning Heating: Use temperature difference reduction to eliminate condensation. Apply Anti-Fog Spray: Use preventive products like anti-fog spray to form a protective film, effectively preventing water vapor from condensing on the glass and forming fog. Open Windows for Airflow: Open both side windows to create airflow between the inside and outside of the car, reducing the temperature difference. Rear Window Heating: Use hot air to dry the glass. Reasons for Car Window Fogging: There is a temperature difference between the inside and outside of the car. If the temperatures differ, 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 fog. Methods to Defog Car Windows: Press the defog button, turn on the air conditioning cooling (A/C) switch, set the temperature to the lowest, and use the external circulation mode to defog. Both cold and warm air can defog car windows, but warm air works slower than cold air. The most effective method is using cold air, as it blows dry air directly onto the glass, preventing water vapor from condensing and achieving defogging. Other methods include using warm air, applying anti-fog spray, opening windows for airflow, and using rear window heating. 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, if the air conditioning is not turned on promptly, the high humidity from exhaled breath can quickly cause the windshield to fog up. Turning on the air conditioning to blow cold air onto the windshield and using the dehumidification function can quickly remove the fog. If the humidity is too high and the air conditioning is ineffective, slightly opening the windows can rapidly reduce the humidity inside the car. Combining this with the air conditioning can speed up the process. Air Conditioning Heating: Use temperature difference reduction to eliminate condensation. In winter, blowing warm air onto the glass quickly raises the temperature of the front glass, reducing the temperature difference between the inner and outer surfaces of the window and preventing excessive fogging. However, 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. Avoid setting the air conditioning to the coldest temperature, as prolonged use can cause frost to form on the outer surface of the windshield. Apply Anti-Fog Spray: Spray a small amount of anti-fog spray onto the car windows and wipe it clean to remove dirt and stains. This also leaves a thin, transparent protective film on the glass, effectively preventing water vapor from condensing and forming fog, especially useful in cold winters. Alternatives to anti-fog spray include dish soap, soapy water, glycerin, alcohol, or saltwater. After applying, let it dry and then wipe off any excess with a soft cloth. This can keep the windows fog-free for several days. Open Windows for Airflow: If the fog inside the car is not too heavy, opening both side windows can create airflow between the inside and outside of the car, reducing the temperature difference and gradually dissipating the fog. This method works on the same principle as using cold air from the air conditioning. However, opening windows has obvious drawbacks, such as being unusable 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. Turning on the rear window heating switch will usually clear the fog within about a minute.
I've been driving for many years, and fogging on the windshield is a common nuisance, especially when getting in the car on rainy days or in winter. I usually turn on the air conditioning defogging mode as soon as I start the engine, adjust the air direction to blow at the front glass, and set the fan speed higher to let cold or warm air disperse the fog. A slightly higher temperature helps speed up dehumidification. Opening the window a bit for ventilation also aids air circulation and reduces interior humidity. To prevent fogging, I regularly use anti-fog spray to wipe the inside of the glass, which works great; I also avoid leaving wet clothes or umbrellas in the car to maintain a dry environment. Cleaning the inside of the glass once a month reduces dust absorbing moisture, significantly lowering the chance of fogging. Before long drives, I check that the air conditioning system is working properly to avoid issues midway. Taking care of these small details regularly makes driving much more worry-free.
