In winter rainy days, should the defogging use internal or external air circulation?
2 Answers
In winter, when using warm air for defogging, you can first adjust the air circulation mode to external circulation to reduce the temperature difference between the inside and outside of the car. After waiting for a few minutes, switch to internal circulation mode. Using anti-fog spray: When using defogging spray, car owners only need to spray it evenly on the glass surface and then wipe it clean with a dry towel. After wiping, a protective film will remain on the glass surface, altering the surface tension of water molecules and causing fog droplets to coalesce into larger water droplets, thus not obstructing the view. This method is also applicable to other car glass surfaces, especially the exterior rearview mirrors. Homemade defogging spray with dish soap: Mix dish soap with water in a 1:6 ratio, put it in a bottle, and spray and wipe it before traveling. The effect is comparable to commercially available defogging sprays, though the durability is slightly inferior.
Last winter when I was driving home in the rain, my car windows suddenly fogged up completely, making it almost impossible to see the road. After thinking about this issue, I realized that defogging requires using the external air circulation. Because humidity inside the car is high on rainy days, human breathing causes fogging. External circulation brings in dry air from outside to remove the moisture inside. If you use internal circulation, you're just recirculating the humid air inside, which will make the fog worse. My usual method is to first turn on external circulation, then press the defog button with the fan at maximum speed blowing on the front windshield - the fog clears in about two to three minutes. Setting the temperature to around 23 degrees is most comfortable - if it's too hot, the temperature difference between inside and outside the glass can actually cause new fog to form. Opening the windows slightly while defogging helps with ventilation too, even though it's a bit colder - safety comes first after all.
