How to Deal with Foggy Car Windows in Winter?

[Patel]

Press the defogging button, turn on the air conditioning (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 car windows, but warm air works 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 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 fogging. When car windows fog up, turn on the external circulation. The reason 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 in the form of tiny water droplets, forming 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 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 dehumidifying 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 window to quickly reduce the humidity inside the car. Of course, you can also use it in combination with the air conditioning for faster results. Air conditioning heating: 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 glass, which can prevent excessive fogging on the windshield in time. However, it should be noted that the temperature of the rear and side windows rises 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 defrosting. 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 cleaning the glass, a thin transparent protective film is formed on the glass, which can effectively prevent 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, use chamois or a soft dry cloth to wipe off excess fibers, which can keep the car windows from fogging up for several days. Opening windows for convection: If the fog inside the car is not heavy, you can open the windows on both sides to create convection between the inside and outside air, reducing the temperature difference and allowing the fog to disappear slowly. The principle of this method is the same as using cold air from the air conditioning. The downside of opening windows for convection 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 electric heating function, although the button positions may vary, the function is the same. Turn on the window heating switch, and the fog on the rear window will disappear in about a minute.

[Susan]

Foggy windows during winter driving can be really annoying, especially on those freezing cold days up north. I think it's mainly caused by the moisture from passengers' breath hitting the cold glass. The most straightforward solution is to use the air conditioning's dehumidification function—just press the AUTO button or adjust the vents to direct air toward the windshield. The AC will dry out the air, and the fog should clear up in a minute or two. For older cars without automatic features, cracking open a window can help in a pinch. Lower the window slightly to allow airflow between the inside and outside, but make sure to stay warm and avoid freezing. Placing some desiccants in the car, like dehumidifying bags bought online, or wiping the windows before driving in winter can also help prevent fogging, and it works pretty well. My advice is not to panic when fog appears—stay focused on driving safely. If it gets too bad, just pull over, deal with it, and then continue your trip.