Should You Use Hot or Cold Air to Defog a Car?
2 Answers
Both hot and cold air can be used to defog a car, but cold air works faster, though it may cause fogging to recur. Warm air defogs more slowly but eliminates the risk of recurring fogging. The rear windshield is defogged using heating wires, while the front windshield cannot accommodate these wires, so the car's air conditioning system is used for defogging. There are air vents located below the front windshield that direct airflow onto it. The air conditioning control panel also features a windshield defogging button. In winter, warm air is typically used to defog the front windshield, while in summer, cold air is generally preferred.
I've encountered this issue many times, especially when getting into the car in winter - the windshield fogs up instantly. My habit is to turn on the cold air for a few seconds first, and the fog clears immediately, it's super fast. However, for long drives or cold weather, keeping the cold air on is too uncomfortable, so I switch to warm air. Although the fog might worsen initially, persisting for a minute or two shows results, plus the car gets nice and warm. The key is to press the AC button to activate the dehumidification function - this works much better than just using the warm air. By the way, a reminder: don't use recirculation mode, otherwise the moisture can't escape and the fogging worsens. Using fresh air mode with vents directed at the windshield is the right approach. It's also handy to keep a defogging spray in the car - one application can last for about a month.
