Why Does Turning on Defogging Make the Fog Worse?

[BarrettMarie]

When the outside temperature is low and the interior heating is on, the temperature inside the car becomes higher, leading to condensation. The water vapor then forms tiny droplets on the cold glass, creating fog. Here are some methods to remove fog: 1. Cold Air Blowing on the Windshield: Lowering the interior temperature and blowing cold air creates a dry barrier on the windshield, preventing water molecules from forming fog. 2. Opening Windows: This quickly balances the temperature difference inside and outside the car and removes moisture from the glass, achieving defogging. 3. Hot Air Defogging: Initially, turning on the hot air increases the temperature difference between the moisture and the glass, making the fog worse temporarily. There will be a delay before the defogging effect takes place.