Why Should You Turn Off the Air Conditioner When the Car Is Turned Off?
2 Answers
The reason for turning off the air conditioner when the car is turned off is: After the engine is turned off, it can no longer drive the compressor to operate, so the air conditioner cannot provide cooling at this time. If the air conditioner continues to run after the engine is turned off, it will reduce the battery's lifespan. Cars are equipped with batteries, and when the engine is not running, the battery supplies power to all electronic devices in the car and is also responsible for starting the engine. Once the engine is started, the alternator takes over to power all electronic devices and can also recharge the battery. Leaving the air conditioner on after the engine is turned off will decrease the battery's lifespan and may even drain the battery. The cooling principle of a car's air conditioner is quite simple: when the AC button is pressed, the compressor clutch engages, and the engine drives the compressor to operate.
Turning off the AC before shutting down the engine is something I've learned from driving experience. If the AC remains on when the car is off, it will continuously draw power from the battery, especially noticeable when the fan is running in summer or winter. With limited battery capacity, continuous power drain will gradually discharge it. If the battery doesn't have enough power when you next start the car, the engine might fail to start. Calling for a tow truck or jump-starting assistance would not only be troublesome but also costly. Additionally, if the AC is on during startup, the system detects the extra load, increasing the burden on the starter motor, which could damage components like fuses or the starter itself. Over time, this practice can also shorten the lifespan of the AC compressor due to poor oil circulation after the engine stops. That's why I make it a habit to check the AC switch before turning off the engine—this small routine can prevent major issues.
