Why can't Mercedes-Benz keep the air recirculation mode on all the time?
4 Answers
Because keeping the air recirculation mode on for a long time when the air conditioner is turned on will cause the air inside the car to not circulate. It is necessary to appropriately turn on the external circulation to promote air circulation, keep the air inside the car fresh, and avoid air turbidity. The principle of internal circulation is that the air circulates in the closed space inside the car, which causes the oxygen content in the car to continue to decrease. Moreover, if the gasoline in the cylinder does not burn completely, the unburned carbon monoxide from the engine may also leak into the compartment. Therefore, the air quality in the car will become worse and worse. The use of internal and external circulation should be combined with the air conditioner and heating, as well as environmental factors, to make a judgment. Taking the winter inside the car as an example, when the vehicle turns on the air conditioner, it is necessary to turn on the internal circulation and turn off the external circulation, because once the external circulation is turned on, the same situation will be formed inside and outside the car, and there will be a certain degree of air flow between them, which will affect the circulation use of the vehicle, and this circulation is not conducive to the use of the vehicle.
I've been driving for over a decade and often encounter Mercedes-Benz owners asking why they can't keep the air recirculation on all the time. It's actually a safety consideration. The recirculation mode circulates air inside the car without bringing in fresh air from outside, which can temporarily block external pollution, save fuel, and provide comfort. However, if left on continuously, the air inside the car becomes increasingly stuffy, and the buildup of carbon dioxide can easily cause drowsiness or headaches, especially during long-distance driving, which is particularly dangerous. Moreover, moisture can't escape from the car, leading to fogged-up windows, especially in winter or rainy weather, which can severely obstruct visibility. Mercedes-Benz systems are designed to automatically switch to fresh air intake periodically, maintaining a healthy environment. Additionally, continuous use of recirculation can cause the air filter to clog prematurely, leading to more maintenance hassle and costs. My advice is to manually activate it when entering tunnels or in heavy traffic, then switch back afterward—safety first.
As a young car enthusiast who loves modifying vehicles, I've researched and found that Mercedes-Benz can't maintain recirculation mode indefinitely mainly due to technical limitations and user protection. The recirculation mode allows the AC to cycle only the cabin air, enabling faster temperature control and better energy efficiency. However, it completely seals off external air intake – prolonged use leads to stale air with decreasing oxygen levels, causing faster fatigue. If someone smokes or there are odors in the car, they get trapped. Mercedes' intelligent climate control automatically switches to fresh air mode for a few seconds periodically to ensure air refreshment, preventing CO2 buildup or window fogging. This is actually an automated safety feature that saves us from potential manual operation errors. During my modification attempts, I've tested forcing recirculation mode, which triggered system warnings or reduced efficiency – definitely not worth it. Personally, I only activate it briefly in heavy traffic with excessive exhaust fumes, otherwise letting the automatic system handle it.
From the perspective of daily car use, the reason why the Mercedes-Benz air conditioning's recirculation mode cannot be left on continuously is to ensure comfort and safety. When recirculation is activated, the air inside the car is sealed and circulated, which can quickly cool down or filter out dust in a short time. However, prolonged use is not advisable because the lack of fresh air leads to moisture and odor buildup, causing frequent window fogging and impaired visibility. Especially during rainy seasons or cold weather, this can easily lead to accidents. The Mercedes-Benz system automatically switches back to fresh air mode to introduce new air and maintain a healthy balance, which is crucial. During regular driving, I occasionally manually activate recirculation to avoid external odors, but by default, letting it operate automatically is more convenient and hassle-free.
