In summer, should you turn on the heater or the air conditioner to remove fog inside the car?
2 Answers
In summer, turn on the air conditioner to remove fog inside the car. Principle of using cold air to defog: On rainy days, the most common method to deal with fogging on the windshield while driving is to turn on the air conditioner and direct it to blow onto the front windshield. The cold air quickly disperses the fog on the glass, providing a fast and direct effect. This happens because the cold air creates a "cold air film" on the glass surface, preventing carbon dioxide from condensing on the glass, thus achieving the defogging effect. Do not use hot air to defog in winter: Hot air can also remove fog, but if you use hot air to defog the front windshield on a rainy day, it will actually worsen the fogging. Right after turning on the hot air, the front windshield may immediately become like "frosted glass." Therefore, if you are driving and the windows fog up due to rain, you should not use hot air to defog.
In summer, when fogging occurs inside the car, especially during high temperatures, as a frequent driver, my first choice is to turn on the air conditioning with cold air. I remember one weekend trip when the car was cool and comfortable with the AC on, but suddenly, on a rainy day, fog covered the windshield, making it impossible to see anything. I immediately turned the cold air conditioning to the lowest temperature and directed the vents toward the glass. In less than two minutes, the fog dissipated. The principle is that in summer, the outside is hot while the inside of the car is cold due to the AC, creating a temperature difference that causes condensation on the glass. Cold air can quickly reduce temperature and humidity, eliminating the condensation. Using warm air would only make the car stuffier, increase fuel consumption, and be less effective than cold air. I also recommend turning on the recirculation mode to help dehumidify more efficiently. For safety, don’t hesitate—turn on the cold air as soon as fog appears. Making it a habit can prevent risks caused by blurred vision.
