Should I Use Hot or Cold Air to Defog the Car?
4 Answers
In winter, when fogging occurs inside the car, warm air should be used to defog. If fogging occurs in summer, cold air should be used. Hot air can also defog, but it may take a longer time. Whether it's summer or winter, opening the car windows can quickly defog the car. Here are some additional tips on defogging: 1. Open windows for convection: Opening windows for convection is a convenient and quick method to defog by lowering the temperature inside the car. However, this method has certain limitations and is not practical in rainy, snowy, or heavily foggy weather. 2. Use the rear windshield and side mirrors for defogging: Currently, many car models are equipped with rear windshield heating features, which can clear fog in about a minute.
I've been driving for so many years and have plenty of experience with defogging. When the weather is cold, I usually blast the cold air first to instantly disperse the fog—visibility clears up immediately, but the car gets unbearably cold after a while. Once the engine warms up, I switch to hot air. Although it gets blurrier for the first few minutes, persisting with it will clear all the fog while keeping the cabin warm and cozy. Remember to press the A/C button when using the AC—it dehumidifies, and that’s the key. Set the airflow toward the windshield. In winter, start with external circulation to ventilate, then switch to internal circulation to retain warmth. In summer, cold air plus A/C is the easiest—no need for hot air at all. In short, use cold air as an emergency fix when you first get in the car, then switch to hot air after driving for a while—that’s the golden rule.
As a parent who frequently shuttles children, comfort must be considered when defogging. Hot air is definitely my top choice, especially in the cold winter months. The warm breeze blows gently, and the fog inside the car slowly dissipates. However, remember to wait until the engine warms up before turning on the hot air, otherwise the effect will be poor. Turning on the A/C button is crucial as it activates the dehumidification function, doubling the effectiveness when combined with the windshield vents. For short trips, cold air works quickly, but children catching a cold breeze can easily get sick. On rainy days, I make sure to turn on the air circulation ten minutes in advance to avoid frantic adjustments while driving, which could compromise safety. Also, flexibly switch between internal and external circulation—avoid external circulation if the outside air is too humid.
Buddy, I've tried it many times, cold air defogging works instantly! Press the defog button, turn up the fan speed, and rotate to the blue cold air zone—you'll see the road clearly in three seconds. This trick is super refreshing in summer, killing two birds with one stone by cooling and defogging. I've also tried hot air, but waiting for the engine to warm up in winter is too much hassle, and the fog actually gets worse at first. However, using hot air on long drives is indeed comfortable—no shivering from the cold. The key is to press the A/C button; without this dehumidification function, the fog won't clear for ages. I always keep anti-fog spray in my car for emergencies. Spray it on the glass on rainy days, then blast cold air—double the effort, half the trouble.
