Should you keep the air conditioner on after turning off the engine?

With summers at the tip of commencement, the most concerned aspect of a car is the air-con system. And one of the most common confusions of many car owners is whether they should use the air conditioner even after turning off the engine, to save a bit of the precious fuel. Many people tend to keep the air conditioner on even after turning off their engine like while standing still in traffic. The comfort that you might feel while doing this might be a half-executed attempt at the best, as the air conditioner doesn’t work at its best capacity in such a situation.

To get into the technical aspect of this fact, when you turn off the engine, the compressor of the air-con system also turns off. In such a case, it will not rotate to pressurise the system. Turning off the engine will also bring the engine fan belt to rest, and in such a case, the compressor will also not rotate as this very fan belt links it. Due to no movement of the compressor, the cooling effect generated by the heat exchange between evaporator and condenser within the system will not be there in existence. If the compressor had been in work, it would have provided pressure to both these components and move refrigerant from the hot side (condenser) to the cold side (evaporator).

So, when you do turn on the button of the air conditioner, the blower fan will start rotating and circulate the air engulfed within the car cabin, but not be able to circulate the cold air as it has not been generated. There is another downside of the practice of using the air conditioner system after you have turned off the engine. When the engine is in the off mode, the blower motor draws power from the battery charge. Due to this, the prolonged use of the air conditioner will cause the blower motor to draw the limited amount of battery charge. This condition will gradually drain the battery, due to which you might be left stranded in the middle of your journey or be unable to start the engine.

So, next time, whenever you want to enjoy the cooling effect of the air conditioner, it is advisable to first turn on the engine. Yes, it will consume a little bit of fuel, but it is in the betterment of the longevity of the motor, battery, and air conditioner system in a whole.