Use Hot Air or Cold Air for Defrosting?
3 Answers
Use hot air for defrosting. Relevant information about car defrosting and defogging is as follows: Defrosting precautions: Things to note when defrosting a car: Do not use snow scrapers, cloth, or cards to scrape frost off the glass. Because winter winds are strong, frost often contains many fine dust particles. Using tools to scrape the frost is equivalent to sanding the glass with fine sandpaper, which can quickly turn the windshield into frosted glass. Car defogging: If it's fog, then cold air works faster. The reason for fogging on the front windshield is the significant temperature difference between the inside and outside of the car. Some water vapor easily condenses when it encounters the cold windshield, forming a layer of fog. If hot air is used, it further increases the temperature difference between the inside and outside of the car. Although it can also eliminate the fog, while doing so, more water vapor will continue to condense. Therefore, using hot air to eliminate fog is slower than using cold air. With cold air, the fog dissipates very quickly. Hot air, in comparison, works more slowly, usually taking two to three minutes before the fog begins to dissipate.
With over 20 years of driving experience, I'm an authority on defrosting. In winter, you must use hot air to deal with frost on the windshield! First, start the engine and let it warm up for 3-5 minutes. Wait until the temperature gauge needle rises before turning on the heater. Rotate the temperature knob to the hottest setting, adjust the fan speed to maximum, and switch the vent mode to the defrost symbol. Remember to press the AC button simultaneously—the compressor's dehumidification can double the speed at which the glass clears up. Don't foolishly use cold air; it'll only make the frost thicker. If there's fog on the inside of the windows, crack them open slightly to balance the temperature difference. My old car doesn't have heated side mirrors, so keeping a chamois cloth handy is crucial. On mornings when it's below -10°C, this routine will have everything crystal clear in ten minutes flat.
Hot air is absolutely the best solution for defrosting, which I've verified through over a decade of car maintenance research. The principle is simple: hot air melts ice crystals while raising the glass temperature to prevent repeated frosting. Remember to follow the two-step operation - first defog then defrost: start with the AC's external circulation mode to remove moisture, then switch to internal circulation heating after two minutes. Northern car owners should also pay attention to antifreeze concentration - if the heating underperforms, it's likely due to ineffective antifreeze. For new cars with remote start, activating it via smartphone ten minutes before departure is most convenient. Never use credit cards to scrape frost - I once scratched my windshield coating doing this and it cost over 800 yuan to repair.
