Should You Use Internal or External Air Circulation for Defogging in Winter Rainy Days?

[BeauDella]

Use external air circulation for defogging in winter rainy days. Apply anti-fog spray: When using a defogging spray, simply spray it evenly on the glass surface and 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 preventing obstruction of vision. This method is also suitable for other car glass surfaces, especially the exterior rearview mirrors. Homemade defogging solution with dish soap: If you forget to buy defogging spray and need a temporary solution, mixing dish soap with water is a good alternative. Combine dish soap and water in a 1:6 ratio, put it in a bottle, and spray and wipe before driving. The effect is comparable to commercial defogging sprays, though the durability is slightly less.

[DelBrianna]

Having driven for over a decade, I've found that using the external air circulation is a must for defogging in winter or rainy days! When there are many people in the car, the humidity is high, and the warm breath exhaled turns into fog upon hitting the cold glass. The internal circulation just blows the humid air around, failing to dissipate the moisture. The external circulation draws in dry, cold air, working effectively with the air conditioning's dehumidification. The operation is straightforward: start the air conditioning in AUTO mode, adjust the temperature to a comfortable range, press the windshield defogging button, and the system automatically switches to external circulation. Once the fog clears, switch back to internal circulation to retain warmth. Remember, the key to defogging is quickly reducing humidity, and external circulation is the most reliable choice.

[Emily]

Last time when I was driving to pick up my kid from school in heavy rain, the windows suddenly turned completely foggy, which scared me into researching the issue. Never use the recirculation mode for defogging—that's like trapping moisture inside the car and recirculating it. You should turn on the fresh air mode to let dry outside air in. My routine is to first press the MAX defog button, then manually adjust the temperature to around 24°C, with the fan automatically set to maximum for the best effect. Once the windshield is clear, switch back to recirculation mode to retain warmth. On rainy or snowy days, I recommend turning on the fresh air mode five minutes in advance to preheat the car—this reduces temperature differences and minimizes fogging. Also, remember to replace the cabin air filter regularly, as a clogged one can reduce dehumidification efficiency.

[LaDavid]

When the windshield fogs up on rainy days, don’t hesitate to switch to external air circulation. Internal circulation only traps more moisture inside the car. Turning on the AC is crucial, as the compressor’s operation effectively removes humidity. Setting the temperature around 22°C is sufficient, and make sure the air vents are directed at the glass. During my commute, I press the defog button to let the AC automatically switch to external circulation. Once the windshield clears, I manually switch back to internal circulation to save fuel. Another tip: Open the windows for a few seconds before driving to let out moisture, which helps prevent fogging.

[LorenzoMarie]

As a car owner in the north, defogging in winter is crucial. On rainy days when fogging occurs, decisively turn on the external air circulation combined with the air conditioning dehumidification. The principle is simple: moisture inside the car condenses into water droplets on the cold glass, and only external circulation can introduce dry air. As soon as I get in the car, I press the AUTO button to activate the automatic air conditioning, setting the temperature between 22-24 degrees for optimal performance. When the defog button lights up, the system automatically switches to external circulation mode. Don't rush to turn on internal circulation for warmth, as it will prolong the defogging time. It usually takes about three to five minutes for the fog to dissipate, after which you can switch to internal circulation. Additionally, wiping dry the water on your shoe soles before driving on rainy or snowy days can also help reduce humidity inside the car.