Why Turn Off the Air Conditioner When the Car is Turned Off?

2 Answers
DelSerenity
07/25/25 9:45am
Turning off the air conditioner when the car is turned off is because the engine can no longer drive the compressor to operate after shutdown, so the air conditioner cannot cool 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 that power all electronic devices when the engine is not running, and the battery is also responsible for starting the engine. If the air conditioner is left on after the engine is turned off, it will decrease the battery's lifespan and may also lead to the battery draining. If the battery is dead, the engine cannot be started. The cooling principle of a car air conditioner is quite simple. When the AC button is pressed, the compressor clutch engages, allowing the engine to drive the compressor. The compressor continuously compresses the refrigerant and delivers it to the evaporator. Inside the evaporator, the refrigerant absorbs heat and expands, cooling the evaporator. The cooled evaporator then cools the air blown by the blower, resulting in cold air coming out of the air vents.
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DelAubrey
08/11/25 7:26pm
As someone who frequently helps friends with car repairs, I must remind everyone that turning off the air conditioning before shutting down the engine is really important. This is because at the moment of engine startup, the air conditioning system places an additional load on the battery, which can cause a sudden voltage drop. If this persists, the battery may age prematurely or even fail. I've seen many cases where owners complain about their batteries not lasting long, only to find out later that it was due to the habit of not turning off the air conditioning before shutting down the engine. This is especially important for older vehicles, as the increased startup load can cause noticeable stuttering sounds and affect startup stability. Additionally, the air conditioning compressor relies on engine operation for lubrication, and forcing it on during startup can wear out internal components, leading to costly and time-consuming repairs. I always recommend turning off the air conditioning a few seconds before stopping the car and waiting until the engine runs smoothly before turning it back on. This protects the equipment and saves money. Remembering this small detail can significantly extend your vehicle's lifespan.
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