What are good methods to solve car window fogging?

[DeCollin]

Car window fogging can be solved in the following ways: Press the defogger button, turn on the air conditioning cooling (A/C) switch, and activate the external circulation to remove fog. Use the air conditioning cooling and dehumidification function to reduce air humidity and eliminate fog. Use the method of reducing the temperature difference to remove condensation. Spray anti-fog agents to prevent dirt and stains on the windows. Open windows for convection; the air inside and outside the car will form a convection current, reducing the temperature difference and gradually dissipating the fog. 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 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 droplets, resulting in fog. Press the defogger button, turn on the air conditioning cooling (A/C) switch, set the temperature to the lowest, and activate the external circulation to remove fog. 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 to use 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 of using warm air is the same as 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. Methods to defog car windows: Air conditioning cooling: Use the air conditioning cooling and dehumidification function to reduce air humidity and eliminate fog. In summer, especially when multiple people enter the car, if the air conditioning is not turned on promptly, the humidity from exhaled breath can quickly cause the windshield to fog up. At this time, turn on the air conditioning to blow cold air onto the windshield, using the dehumidification function to quickly remove 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 will yield faster results. Air conditioning warm air: Use the method of reducing the temperature difference to remove condensation. In winter, blow warm air onto the windshield to quickly raise its temperature and reduce the temperature difference between the inner and outer surfaces of the glass, preventing excessive fogging. However, 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. Do not set the air conditioning temperature to the coldest position, as this may cause frost to form on the outer surface of the windshield over time. Spray 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. While polishing the glass, a thin transparent protective film is formed, effectively preventing water vapor from condensing on the glass and forming fog, especially suitable for cold winters. Alternatives to anti-fog agents include dish soap, soapy water, glycerin, alcohol, or salt water. After drying, use chamois or a soft dry cloth to remove excess fibers, ensuring the car windows remain fog-free for several days. Open windows for convection: If the fog inside the car is not too heavy, open the side windows to allow air inside and outside the car to form a convection current, 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 for convection is obvious: it cannot be used during rain or snow, on highways, or when the fog is heavy.

[DiIsabelle]

Every time it rains or during winter drives, I encounter foggy windows with blurred vision, which is quite dangerous. The quickest method I've learned is to press the defog button—the one with the windshield icon. Pressing it automatically turns on the A/C cooling and directs the maximum airflow toward the windshield, clearing the fog in minutes. If there's no button, manually turn the air conditioning to cold mode, adjust the vents to blow toward the windshield, and use the recirculation switch to regulate outside air for a quick effect. I usually keep the interior of the windshield clean, as oil residue can trap fog, so I use a microfiber cloth or defogger to wipe it down as prevention. In summer, before entering a hot car, I open the windows for ventilation before starting; in winter, I preheat the car in advance to avoid large temperature differences that cause fogging. Remember, safety first—don’t brake suddenly when fogging occurs; instead, slowly pull over to handle it. Also, check the cabin air filter and replace it regularly to improve defogging efficiency, especially during severe smog days. These small habits make my driving safer and hassle-free.