What does it mean when the car's internal circulation light is on?
4 Answers
The internal circulation light being on indicates that the internal circulation mode is activated. Internal circulation button: If the internal and external circulation buttons are separate, each controls its respective circulation state. The light being on means that function mode is active. If the internal and external circulation functions are on the same button, when the indicator light is on, it is in internal circulation mode. When the indicator light is off, it is in external circulation mode. Function of internal circulation: The purpose of the air conditioning internal circulation mode is to prevent outside air from entering the car. When the outside temperature is very high or very low, selecting the air internal circulation mode allows the air conditioning system to operate in this mode for a short time, quickly lowering or raising the temperature inside the car. If equipped with an air quality sensor, when the system detects an increase in the concentration of harmful substances in the outside air, it will immediately and automatically activate the air internal circulation mode to prevent outside air from being drawn into the car. Once the concentration of harmful substances in the outside air decreases to normal levels, the system will immediately and automatically turn off the air internal circulation mode, allowing fresh air to enter the car again.
Last time I drove long distance, I paid special attention to the recirculation light. When it's on, it means the AC system is cutting off outside air intake and only circulating air inside the vehicle. This mode is particularly suitable when passing through dusty sections or heavy traffic with exhaust fumes, as it significantly reduces dust and odors entering the cabin. However, be aware that prolonged use of recirculation mode can increase CO2 concentration inside, making drivers drowsy - it's recommended to switch back to fresh air mode when highway air quality is good. Some newer cars now feature automatic switching functionality that adjusts based on air quality sensors, which is quite intelligent.
I noticed many friends don't quite understand the actual meaning of the recirculation light. Simply put, it means the AC system closes the external air intake, like preventing exhaust fumes from entering when driving through tunnels. Using this mode also cools down the car much faster when running AC in summer. However, three reminders: first, don't keep it on during rainy days to avoid fogging up the windows; second, it's better to switch to fresh air mode for ventilation after driving for over 30 minutes; third, never activate it when sleeping in the car to prevent oxygen deprivation. Many modern vehicles now feature automatic timer switching functions to address this issue.
Veteran drivers know that when this small light comes on, it means the vehicle has activated the air recirculation mode. Its greatest value lies in two scenarios: first, when driving through construction sites or on hazy days, it can block 95% of external pollutants; second, when using the air conditioning in summer, it cools the cabin twice as fast as the external circulation mode. However, it has a hidden issue—poor humidity regulation. Once, I drove with the recirculation mode on continuously for 40 minutes on a rainy day, and the windshield fogged up suddenly, almost obscuring my view. Now, I’ve developed the habit of always turning on the A/C for dehumidification when using recirculation on hazy days—ensuring both health and safety.
