How to Solve Foggy Windows on Rainy Days?

[MacLuke]

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 to use cold air, which 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 it's important to note that warm air should not be used for defogging on rainy days, as it may initially worsen the fog. Always use external circulation when defogging car windows. The reason for foggy car windows: 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 and form tiny water 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 turning on the air conditioning promptly, the exhaled air has high humidity, and the windshield can quickly fog up. In this case, turn on the air conditioning to blow cold air onto the windshield. Using the air conditioning's dehumidifying function, the fog on the windshield can be removed quickly. However, if the humidity is too high and the air conditioning is not effective, slightly opening the windows can quickly reduce the humidity inside the car. Combining this with the air conditioning can speed up the process. Air Conditioning Warm Air: Use the method of reducing the temperature difference to remove fog. In winter, blowing warm air onto the glass quickly raises the temperature of the windshield, reducing the temperature difference between the inside and outside surfaces of the glass. This can prevent excessive fogging on the windshield. However, it's worth noting that 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 temperature to the coldest position, as this can cause frost to form on the outside of the windshield over time. Applying Anti-Fog Spray or Other Preventative Measures: 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 forms on the surface, effectively preventing water vapor from condensing and forming fog. This is especially useful in cold winters. Alternatives to anti-fog spray include dish soap, soapy water, glycerin, alcohol, or saline solution. After applying and letting it dry, wipe off any excess with a chamois or soft dry cloth. This can keep the car windows fog-free for several days. Opening Windows for Airflow: If the fog inside the car is not too heavy, you can open the windows on both sides to create airflow between the inside and outside of the car. This reduces the temperature difference and gradually eliminates the fog. The principle of this method is the same as using cold air from the air conditioning. However, the downside of opening windows is obvious: it cannot be used during rain, snow, on highways, or when the fog is heavy. Rear Windshield Heating: Most cars have a rear windshield heating function, though the button location may vary. The function is the same. Turn on the windshield heating switch, and the fog on the rear windshield will disappear in about a minute.