Can the air conditioner be turned on when the engine is off?

[VanElla]

It is not possible to turn on the air conditioner when the engine is off. Engine: The car engine is the device that provides power to the vehicle, serving as the heart of the car and determining its power, fuel efficiency, stability, and environmental performance. Depending on the power source, car engines can be classified into diesel engines, gasoline engines, electric vehicle motors, and hybrid systems, among others. Engine Structure: The engine consists of two main mechanisms: the crankshaft-connecting rod structure and the valve train structure, along with five major systems: cooling, lubrication, ignition, fuel supply, and starting systems. Key components include the cylinder block, cylinder head, piston, and piston pin.

[ValeriaLynn]

Last time I went camping, I tried running the AC with the engine off and nearly killed the battery. In regular gas cars, once you turn off the engine, the compressor stops working—only the blower keeps running, draining the battery entirely. Running it for half an hour while waiting in summer dimmed the dashboard lights, forcing me to call for a jump-start. Even in electric vehicles where the compressor is electrically powered, using AC with the engine off still drains the battery, potentially leaving the low-voltage battery too weak to start the car after prolonged use. If you really need temporary cooling, it’s better to idle the engine for ten minutes to cool down quickly before shutting it off. Replacing a battery costs at least 600-700 RMB—hardly worth it just for some AC. A handheld mini-fan is a far more practical backup.

[SanDakota]

Once when picking up my child from school on a hot day, I turned off the engine and waited in the car with the AC on. It felt cool at first, but after ten minutes the airflow weakened, and when I turned the key the car wouldn't start! The mechanic explained that the AC blower relies entirely on the battery - a typical 12V car battery only has 45-60 amp-hours capacity, and running just the blower for an hour can drain 20% of the charge. In fuel-powered cars, the compressor belt isn't connected to the engine when idling, so you're just getting natural air circulation. Now in summer I either remotely start the AC to cool the car beforehand, or simply bring cooling pads and sunshades - it's more worry-free and energy-efficient.

[AsherMarie]

Running the AC while the engine is off can severely damage the battery. Although the blower can operate, the cooling function won't work. A lead-acid battery's lifespan drastically decreases after just a few deep discharges. I've measured that a typical car's blower consumes about 150 watts, draining 1.8 amp-hours in just half an hour. When the battery charge drops below 50%, starting the engine becomes difficult, and towing fees often exceed the cost of running the AC. If you must use it briefly, keep it under five minutes—cracking a window is more practical.