Why does the outside of the car window fog up when the air conditioning is on?

[CameronDella]

When the car's air conditioning is turned on, the outside of the window fogs up because the outside temperature is lower than the inside temperature, causing water vapor inside the car to form many tiny water droplets. Since the surface of the windshield is not perfectly smooth, these small water droplets adhere to the windshield. Below are some precautions for using the air conditioning system: 1. Check the cooling effect: The car's air conditioning system is generally unused during winter. Before initial startup, check the belt tension and let the engine idle for a while to observe if it starts normally and check the cooling effect during operation. If it does not start or the cooling effect is unsatisfactory, take it to a service station for inspection. 2. Clean the air conditioning system: The air conditioning system tends to accumulate dust and bacteria during use, so after prolonged use, it should undergo a dust and bacteria removal treatment to ensure the health of the passengers.