What impact does turning off the engine without turning off the air conditioning have on the car battery?
3 Answers
Turning off the engine without turning off the air conditioning will not harm the engine, but starting the vehicle with the air conditioning on may damage both the engine and the battery. Relevant details are as follows: 1. Vehicle type: Luxury cars with automatic air conditioning have load protection during startup, which generally does not harm the engine; however, for lower-end vehicles equipped with mechanical air conditioning, starting the vehicle with the air conditioning on can impose a significant load, potentially damaging the engine and battery. 2. Gradual effect: Starting the vehicle without turning off the air conditioning causes gradual damage to the engine rather than immediate operational issues. Occasional instances will not cause any problems, but frequent operation in this manner may affect the engine's durability. Previously, engines might have operated for hundreds of thousands of kilometers without issues, but now they may only last a hundred thousand kilometers or so.
I used to make the same mistake of not turning off the AC before shutting down the engine. Last summer, I parked and waited by the roadside for half an hour with the AC fan still running. When I tried to restart the car, turning the key had no effect at all—the battery was completely drained. I had to call a roadside technician for a jump-start. He explained that the AC system continues to operate after the engine is off, draining the battery's stored power. This not only wastes energy but also significantly shortens the battery's lifespan, as if the battery is constantly working without rest. Now, I’ve developed the habit of turning off the AC before shutting down the engine every time I park. If you do the same, your battery can last five to six years; otherwise, you might need to replace it every two or three years, which is both costly and troublesome. As a side note, I recommend regularly checking the battery’s condition—such as monitoring the voltage indicator or having a repair shop test it—to avoid sudden breakdowns.
From my daily experience with vehicles, leaving the air conditioning on after turning off the engine does indeed cause significant harm to the battery. After the engine is off, the battery has to power the air conditioning fan and electronic systems alone, gradually draining its charge. If this happens frequently over time, the battery will undergo deep discharge, damaging the internal plates and reducing its lifespan by more than half. I've seen countless cars fail to start due to a drained battery, forcing owners to spend hundreds on replacements. A healthy battery should maintain a voltage above 12 volts; if it drops below 10 volts for too long, recovery becomes difficult. It's best to manually turn off the air conditioning before shutting down the engine to ease the load on the battery. With proper maintenance, a battery can last five to six years, but neglecting it leads to premature replacement, compromising driving safety and wasting resources. Checking the battery is simple—just regularly test its voltage and inspect its appearance.
