How to Deal with Foggy Car Windows on Rainy Autumn Days?
2 Answers
Press the defogging button, turn on the air conditioning (A/C) switch, set the temperature to the lowest, and switch to external circulation to remove fog. 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, which blows dry, cold air directly onto the glass, preventing water vapor from condensing on the surface and achieving defogging. The method for using warm air is the same as cold air, but note that warm air should not be used on rainy days as it can initially worsen the fog. Always use external circulation when defogging car windows. The reasons for foggy car windows: There is a temperature difference between the inside and outside of the car. If the temperatures differ, the side with the lower temperature will have a surface saturated vapor pressure lower than the surrounding environment's vapor pressure, 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 without promptly turning on the air conditioning, the exhaled humid air can quickly cause the windshield to fog up. In this case, turn on the air conditioning to blow cold air onto the windshield, using its dehumidifying function to quickly remove the fog. If the humidity is too high and the air conditioning is ineffective, 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 Heating: Use the method of reducing the temperature difference to remove fog. In winter, blowing warm air onto the glass quickly raises its temperature, reducing the temperature difference between the inner and outer surfaces and preventing heavy fogging. Note that the rear and side windows heat up more slowly, so it takes longer to fully defog them. Whether the air conditioning is automatic or manual, turning it on helps with dehumidification. Avoid setting the temperature to the coldest position, as prolonged use can cause frost to form on the outer surface of the windshield. 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. This creates a thin, transparent protective film that effectively prevents water vapor from condensing into fog, especially useful in cold winters. Alternatives to defogging agents include dish soap, soapy water, glycerin, alcohol, or saline solution. After applying, let it dry and then wipe off any excess 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, opening the side windows can create airflow between the inside and outside, 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, its drawbacks are obvious: it cannot be used during rain, snow, on highways, or when the fog is heavy. Rear Window Heating: Most cars come with a rear window heating function, though the button location may vary. Turning on the rear defroster will clear the fog in about a minute.
In autumn, with frequent rain, fogging on car windows is quite common. Whenever I encounter this, I first turn on the air conditioner's cold air to blow directly at the windshield and outer windows, which quickly removes moisture and dries the air. If the car has a heating defogging function, I turn up the temperature to assist. During rain, I'm hesitant to open windows for fear of getting wet, but cracking them slightly for ventilation also helps. Keeping the windows clean in the long term prevents moisture buildup. It's also important to check if the air filter is too dirty or clogged, as this can affect defogging efficiency. Safety comes first—fogging can obscure the road, so if it's severe, pull over to handle it, ensuring clear visibility before driving again. Remember not to wipe the glass directly with your hands, as it leaves watermarks that are harder to clean. I recommend regularly checking these systems to avoid unexpected delays.
