Should You Turn Off the Internal Circulation When Parking and Turning Off the Engine?
2 Answers
No need to turn it off. After the car is turned off, the entire air conditioning system will not be powered, so leaving it on will not waste electricity. Here is some extended information about internal and external circulation: Principle of External Circulation: The external circulation mode uses a fan to draw air from outside the car into the interior, meaning the air passages between the outside and inside of the car are open. The air blown by the fan comes from outside the car. Even if the fan is not turned on, airflow is still drawn into the car while driving, replenishing fresh air inside the car. Principle of Internal Circulation: The internal circulation mode closes the airflow passages between the inside and outside of the car. Without the fan, there is no airflow circulation. When the fan is turned on, the airflow drawn in comes only from inside the car, creating an internal airflow circulation within the vehicle.
Actually, this issue has been discussed by many experienced drivers. Having driven for over a decade, I've developed the habit of turning off the recirculation mode before shutting off the engine. The main reason is that moisture tends to accumulate in the air conditioning system. If you keep the recirculation mode on after turning off the engine, that dampness gets trapped in the ducts, breeding bacteria over time. The next time you start the car, you're greeted with an unpleasant musty smell. Additionally, during summer when the car interior is hot, suddenly turning on the AC results in poorer cooling performance. Now, I switch to fresh air mode about two or three minutes before reaching my destination to allow fresh air circulation, and I turn off the AC button before shutting off the engine. This way, the cabin air is much fresher the next morning when starting the car, and it's also better for the longevity of the cabin air filter.
