What Happens If the Car's Air Conditioner Is Left On When the Engine Is Off?
2 Answers
Leaving the air conditioner on when the car is turned off can affect both the engine and the battery. This is because the air conditioning system will automatically start working the next time the vehicle is started, placing a burden on the engine and causing an instant high power load. Over time, this can lead to wear and tear on engine components, increased carbon buildup, and battery depletion. Below are some precautions for using a car's air conditioning system: 1. Periodically turn the air conditioner to its maximum setting for about 10 minutes to effectively prevent dust accumulation. 2. Running the air conditioner while parked is inherently harmful. If smoking in the car, be sure to adjust the air ventilation control to the "exhaust" position. 3. Under normal circumstances, the cabin temperature should be adjusted to around 26~27 degrees Celsius for optimal comfort. 4. If the air outlet mode is improperly selected, the cold air blown by the air conditioner may cool high-temperature components that do not require cooling, thereby offsetting the cooling effect. It is best to choose an upward airflow direction, which aligns with the principle of cold air sinking. Additionally, selecting the face-level airflow setting ensures the most uniform cooling effect. 5. When first turning on the air conditioner, use the external circulation mode to lower the cabin temperature, then switch to internal circulation. However, remember to alternate between these two modes periodically.
I've been driving for over a decade, and this is something you really need to pay attention to. If you forget to turn off the AC before shutting down the engine, both the engine and AC will start simultaneously during the next ignition, forcing the battery to handle dual loads. Over time, this can reduce battery life by at least one-third, especially for older batteries that have been in use for three or four years – they might even drain completely and fail to start. I've seen several cars stranded roadside during summer, mostly due to this issue. If the starter motor gets affected too, repairs can easily cost four figures. I've developed a habit now: turning off all electrical devices before shutting down the engine, and waiting about ten seconds after starting before turning on the AC. Your car needs to catch its breath just like we do.
