Why does turning on the defroster also activate the AC?

[ArielLee]

Turning on the defroster and AC simultaneously is because the air blown out by the compressor for defogging is the driest, which can quickly remove fog from the windshield. Here are some methods for defogging car windows: 1. Lower the temperature inside the car by opening the windows or turning on the AC to reduce the temperature difference between the inside and outside of the car. 2. One-touch defogging. Not all vehicles have this feature, but those equipped with it can directly activate one-touch defogging for convenience. 3. Use the heater to reduce humidity inside the car. The effectiveness of the heater depends on the car's water temperature, so you need to wait until the engine warms up to see results. This method is slower than using cold air. 4. Use the AC dehumidification function. In winter, the AC's dehumidification function can also quickly eliminate fog, but it will make the interior colder.