Why should you turn off the air conditioning before turning off the car?
2 Answers
Leaving the air conditioning on after turning off the car can reduce the battery's lifespan. This is because the engine cannot drive the compressor after the car is turned off, making the air conditioning unable to cool. The car's battery powers the air conditioning when the engine is not running. The alternator is the main power source of the car, functioning to supply power to all electrical devices (except the starter) while the engine is running normally, and simultaneously charging the battery. Based on the three-phase stator winding of a conventional alternator, the number of winding turns is increased, and additional terminals are added, along with an extra three-phase bridge rectifier. At low speeds, the output is from the original winding and the additional winding in series, while at higher speeds, only the original three-phase winding provides the output.
As a seasoned driver with over 20 years of experience, I've made it a habit to turn off the air conditioning before shutting down the engine. This isn't being overly cautious—it's genuine care for my beloved car. Here's why: When the AC is running, it draws power from the battery. If you don't turn it off before shutting down, the sudden activation of the AC during the next engine start will put extra strain on the battery. This is especially problematic in cold weather or with older vehicles, potentially leading to premature battery failure. Over time, it can also damage the compressor and engine, increasing repair costs. Additionally, residual moisture in the AC's evaporator after shutdown can breed mold, causing unpleasant odors that affect driving comfort. I've seen many beginners neglect this, resulting in frequent AC system failures or poor cabin air quality—costing them unnecessary money on parts replacement. Adopting this simple practice extends your vehicle's lifespan and maintains cabin cleanliness—it's practical and effective.
