How to Deal with Foggy Car Windows in Winter?
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 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, as it 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 note that warm air should not be used on rainy days as it may initially worsen the fog. Always use external circulation when defogging car windows. The reason for car windows fogging up: There is a 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 in the form of tiny droplets, forming fog. Methods to defog car windows: Air Conditioning (Cold Air): 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. In this case, turn on the air conditioning to blow cold air onto the windshield, using its dehumidification function to quickly remove the fog. 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 warm air to reduce the temperature difference and remove fog. In winter, blowing warm air onto the windshield quickly raises its temperature, reducing the temperature difference between the inside and outside surfaces of the window, thus preventing heavy fogging. However, note 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 temperature to the coldest position, as prolonged use can cause the outer surface of the windshield to fog up. Applying Anti-Fog Spray: Spray a small amount of defogging agent onto the car windows and wipe it clean to remove dirt and stains. This also forms a thin transparent protective film on the glass, effectively preventing water vapor from condensing and forming fog, especially 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 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, open the side windows slightly to allow air to flow between the inside and outside of the car, reducing the temperature difference and gradually eliminating the fog. The principle is the same as using cold air from the air conditioning. However, this method has obvious drawbacks and cannot be used 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. Turn on the rear window heating switch, and the fog will disappear in about a minute.
Driving in winter is most annoying when the windows fog up! As a veteran driver with twenty years of experience, I’ll teach you a few tricks: Before setting off, turn the heater to maximum and direct it at the windows, then wait for the car to warm up before driving. Keep a dry towel in the car to wipe away fog at any time—never use your clothes to wipe, as it will only make things worse. Turning on the air conditioner’s external circulation with a bit of cold air works wonders; though it might feel chilly at first, the fog will clear in about five minutes. Here’s another little secret: buy an anti-fog spray in advance and apply it to the inside of the windows—it can keep fog away for up to two weeks! Never ignore foggy windows—last year, I saw a tragic accident where a new driver couldn’t see the road and crashed into a guardrail.
