Why does the outside of the car glass fog up when the AC is on?

[DeAbel]

The reason for fog forming on the outside of the car glass when the AC is on is that the temperature inside the car is much lower than the outside temperature. When moisture in the outside air comes into contact with the very cold windshield, it condenses into fog. Here is relevant information: Solution: First, you can use the windshield wipers since the fog is on the outside of the glass, where the wipers can be effective. If the fog is heavy and the wipers don't help much, you can also use warm air to blow on the windshield. Adjust the AC temperature to produce warm air, increase the temperature for automatic AC, rotate the direction switch to direct air toward the glass, and the fog will disappear shortly. This happens when the temperature is set too low or the outside weather is humid. Generally, it's best to use the recirculation mode with the AC vents directed toward the feet and head.