Should the Air Conditioning Be Turned Off Before Engine Shutdown?
2 Answers
It is necessary to turn off the air conditioning before engine shutdown. If the air conditioning is not turned off before shutdown, it will automatically restart when the engine is next started, which unnecessarily increases the engine load. However, it is important to note that the external circulation should be turned on either before or after shutdown. 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: 1. Switching between internal and external circulation is possible: Modern vehicle automatic air conditioning systems can switch between internal and external circulation, relying on sensors to detect air quality. 2. The temperature sensor affects automatic air conditioning circulation switching: In lower-end vehicles, the only sensor affecting the automatic air conditioning's circulation switching is the temperature sensor. It transmits the interior temperature and the set temperature to the air conditioning system, which then uses actuators to switch the circulation mode. To activate internal circulation in automatic air conditioning, increase the temperature difference; to activate external circulation, decrease the temperature difference. However, even when the air conditioning automatically switches to internal circulation, there is no indicator light inside the vehicle to signal this.
When I first started driving, the old-timers always reminded me to turn off the air conditioning before shutting off the engine. Once you develop this habit, your car will suffer less. If you don't, the AC will suddenly turn on the next time you start the car, putting extra strain on the engine. Over time, this can lead to starter motor failure or belt tension issues. It's especially noticeable in summer—if you turn off the engine with the AC still running, the compressor will kick in forcefully when you restart, making the car shudder. Plus, turning off the AC reduces residual moisture, preventing mold growth in the ducts and eliminating weird smells from the vents. After decades of driving, I still make it a point to turn off the AC before shutting down the engine—it saves fuel and protects the car. It's a practical habit worth forming, so don't skip it just because it seems like a hassle.
