Should You Use Internal or External Air Circulation When Turning on the Car Heater?
2 Answers
Whether to use internal or external air circulation when turning on the car heater depends on the specific situation: 1. In winter, if you want to quickly heat up the car interior, you can start the engine and drive normally for a while to warm it up. Once the temperature gauge needle reaches the middle position, turn on the heater with internal circulation. Using internal circulation allows the air conditioning to quickly cool or heat the car interior. This not only warms up the car quickly but also avoids putting extra load on the engine, saving fuel. 2. Although continuous internal circulation keeps the car warm, the interior becomes a relatively sealed environment. Prolonged exposure to this environment can lead to oxygen deprivation. Therefore, it's best to switch to external circulation every hour to draw in fresh air from outside. This air then passes through the air conditioning evaporator or heater core, producing cool or warm air respectively.
When I want to stay warm while driving, my go-to method is to first turn on the recirculation mode before switching to fresh air mode. In winter, when starting the car and shivering from the cold, I immediately activate recirculation mode—it recycles the warm air inside the car, heating up much faster than fresh air mode. However, using only recirculation can easily fog up the windows, especially when there’s a big temperature difference, and the fog obstructing the view is dangerous. So once the cabin feels comfortably warm, I switch to fresh air mode to let in outside air, which clears the fog while maintaining ventilation. On highways or in urban areas with heavy air pollution, I extend the recirculation time appropriately to reduce inhaling exhaust fumes, balancing safety and comfort. During long drives, I pay extra attention to switching modes to avoid fatigue, especially since I often drive at night—these habits help me stay alert.
