Should You Use Internal or External Air Circulation When Running the Car AC?
3 Answers
Generally, internal air circulation is more commonly used when running the car AC. Below are detailed introductions to internal and external air circulation in cars: 1. External Air Circulation: This refers to drawing air from outside the vehicle, directing it through the AC system for heating or cooling, and then blowing it out through the vents. External circulation essentially replenishes fresh air to improve the air quality inside the car. It should be used for defrosting in winter or defogging in summer, as the air drawn from outside is richer in oxygen and drier, making it more effective for these purposes. 2. Internal Air Circulation: This involves drawing air from inside the car, creating a cycle of airflow within the vehicle. The primary function of internal circulation is to promptly and effectively block external dust and harmful gases from entering the car. It helps the car warm up faster in winter and cool down quicker when the AC is on in summer. It can also be used during smoggy days. Internal circulation maintains the air inside the car, helping to preserve the interior temperature more effectively.
I always pay attention to switching between the internal and external air circulation when using the car air conditioner. When I first turn on the AC, I use the internal circulation mode to get the cooling effect quickly—the temperature inside the car drops rapidly. After about ten minutes or so, I switch to external circulation to let fresh air in, otherwise sitting for too long can make me feel dizzy and uncomfortable. On the highway, keeping the external circulation on feels more comfortable, and it doesn’t increase wind noise. In traffic jams, I always remember to switch back to internal circulation to prevent exhaust fumes from the car ahead from entering the cabin. For long drives, changing the circulation mode every half hour is the most reasonable approach—it saves fuel while ensuring good air quality. Also, don’t forget to replace the cabin air filter on time, especially during pollen season.
When using the air conditioning, I choose the circulation mode based on specific situations. On scorching summer afternoons when the car is baking hot, I definitely start with recirculation mode to cool down quickly—otherwise, the AC struggles to cool effectively. On nice days, I prefer fresh air mode to keep the cabin ventilated and avoid stuffiness. Near dusty construction sites or during smoggy days, I immediately switch to recirculation to block polluted air. Rainy days require extra attention: fresh air mode can cause fogging, so I pair it with the defogger. Cars with automatic AC are the most hassle-free—just press AUTO, and it adjusts modes as needed after setting the temperature. Don’t forget to clean the AC vents regularly, or you’ll get musty air during ventilation.
