Should the Air Conditioning Be Turned Off Before Shutting Down the Engine?

[MaverickMarie]

It is necessary to turn off the air conditioning before shutting down the engine. If the air conditioning is not turned off before shutting down, it will automatically start the next time the engine is turned on, which unnecessarily increases the engine's load. However, it is important to note that the external circulation should be turned on either before or after shutting down the engine. This is because the evaporator, which has been continuously cooling, will accumulate many small water droplets on its surface after parking. If left unattended, bacteria can grow inside the evaporator over time, leading to a musty odor. Additional information is as follows: Switching between internal and external circulation is possible: Modern vehicle automatic air conditioning systems can switch between internal and external circulation, which is based on sensor detection of air quality. The sensor that affects the automatic air conditioning's circulation switching is the temperature sensor: In lower-end vehicles, the only sensor affecting the automatic air conditioning's circulation switching is the temperature sensor, which transmits the in-car temperature and the set temperature to the air conditioning system. The air conditioning system then switches the circulation mode via actuators. To achieve internal circulation in automatic air conditioning, increase the temperature difference; to achieve external circulation, decrease the temperature difference. However, even if the air conditioning automatically switches to internal circulation, there will be no light indication inside the car.

[HarrisonAnn]

Turning off the air conditioning before shutting down the engine is a good habit. As a seasoned driver with 30 years of experience, I've always practiced this. The reason is that if the AC compressor is still running when you start the engine next time, the sudden load can be substantial, potentially causing a shock to the battery. A shortened battery lifespan means premature replacement, which is costly and unnecessary. Especially in hot summer weather, if the car's AC refrigerant is still operating and the engine is suddenly turned off, it may lead to moisture accumulation in the evaporator. Over time, this can cause mold and unpleasant odors, affecting health. Every time before parking, I turn off the AC in advance and let the fan run for a few minutes to expel any residue. This ensures smoother AC operation the next time I drive and maintains the overall good condition of the car. This simple practice also helps avoid unexpected malfunctions, such as a dead battery preventing startup, which could leave you stranded on the road. Once it becomes a habit, you'll spend less time and money at the repair shop.

[Kyle]

As a dad who often drives my kids around, I find it quite important to turn off the air conditioning before shutting down the engine, mainly for peace of mind and cost savings. If left on, the AC system loses power abruptly, causing a heavy load during the next startup, which can easily damage the battery. Replacing a battery costs over a thousand yuan—enough for a nice family meal. My wife used to complain about a musty smell in the car, and we later discovered it was due to moisture buildup from forgetting to turn off the AC. Now, we make it a habit to turn off the AC one minute early, letting the blower expel the moisture, and the air inside feels much fresher. This simple habit takes no extra time, extends the AC's lifespan, and avoids repair costs. I pay extra attention to this when my kids feel carsick, ensuring a comfortable and safe cabin environment.

[StJayla]

As a newbie who just bought a car a year ago, I used to frequently stall the engine and forget to turn off the AC. Once in a parking lot, my battery almost died—thankfully nothing serious happened. Since then, I've made it a habit to turn off the AC in advance. Although modern cars have protection features, switching it off can reduce the load on the next startup and help protect the battery for longer use. It's a simple operation—just press the button a moment before turning off the engine. Occasionally forgetting isn't a big deal, but forming this habit gives peace of mind. For young people with fast-paced lives, remember this precautionary measure to prevent future issues.