Should You Use Internal or External Air Circulation for Car AC in Winter?
2 Answers
In winter, using the internal air circulation mode for your car's AC allows for rapid cooling or heating inside the vehicle. When outdoor temperatures are extremely low, activating internal circulation helps raise the cabin temperature quickly. External circulation works by drawing outside air into the car through a fan, meaning there's an open air passage between the exterior and interior. Even with the fan turned off, moving vehicles still allow some outside airflow to enter the cabin, replenishing fresh air. Internal circulation closes this airflow channel between inside and outside - without the fan running, there's no air movement, and when the fan operates, it only recirculates existing cabin air. The primary purpose of internal circulation is to effectively block external dust and harmful gases from entering, such as when driving through smoky areas, dust clouds, zones with strong odors, or during heavy traffic where it prevents inhalation of exhaust fumes from preceding vehicles.
As a veteran driver with ten years of experience in the north, I definitely prefer using the recirculation mode for the car heater in winter. Keeping the cold air outside allows the engine's modest warmth to quickly fill the cabin, so I don't even need to turn on the seat heaters. But the window fogging is truly annoying—I have to switch to fresh air mode every five minutes to ventilate, otherwise the glass becomes as opaque as frosted glass. Once, I forgot to switch modes when picking up my child from school, and the fogged-up windows nearly caused a rear-end collision. Now I've learned my lesson: when fogging occurs, I aim the vents at the windshield and alternate evenly between recirculation and fresh air modes for the safest approach.
