Is it necessary to turn on the blower for the external circulation mode?

[Lilliana]

External circulation does not require turning on the blower. Working principle of car air conditioning: The car air conditioning refrigeration system consists of a compressor, condenser, receiver-drier, expansion valve, evaporator, and blower, among other components. These parts are connected by copper pipes (or aluminum pipes) and high-pressure rubber hoses to form a sealed system. Functions of automatic air conditioning: The functions of automatic air conditioning include automatic adjustment of interior temperature and humidity, automatic control of air recirculation and fresh air modes, as well as operation mode and air volume control. The electronic control unit will automatically operate the air conditioning system based on the settings made by the driver or passengers via the buttons on the air conditioning display control panel. It will also adjust the air supply temperature and speed in a timely manner according to the signals input by various sensors to maintain the optimal air environment inside the vehicle.

[Josie]

As someone who frequently helps friends with car-related issues, I've actually tested this scenario. When the external circulation is on, there is indeed a faint airflow from the vents, but without the blower, it's like relying solely on window gaps for ventilation in a room without a fan. The blower is the key component that truly 'draws' outside air into the car, especially noticeable when trying to refresh the air at highway speeds. I remember last summer during a camping trip, a friend complained about stuffiness despite having external circulation on—turns out he had the blower turned off. Now he's developed the habit of always turning on the fan speed button with external circulation, even at the lowest setting, which is three times more effective than relying purely on natural airflow.

[LeFaith]

I've been commuting by car for eight years, and from personal experience, the external air circulation must be used with the blower. The principle is simple: without the blower, the pressure difference between the inside and outside of the car is insufficient, and fresh air simply can't make its way into the cabin. It's like trying to drink through a straw without sucking first. Last month, a colleague complained about a strange smell from the AC. I had him try running the external circulation without the blower for ten minutes, and all that came out was hot air. Later, we found out the AC filter was clogged—but the key takeaway is, if the blower isn't running, you don't even get a chance to diagnose the problem.

[SanJordan]

Experience has taught me that using only the external air circulation without the fan is much less effective. One late night when it was raining, the windshield fogged up. I turned on the external air circulation without the fan to save power, but the fogging actually worsened. Later, I learned that without the fan's airflow, external moisture gets stuck at the air intake and seeps inside. Now I've learned my lesson: whenever I turn on the external air circulation, I always set the fan to its lowest setting. This saves power while ensuring proper air circulation. This practice applies to all vehicle models and is a zero-cost maintenance tip.

[Stephen]

From the perspective of vehicle engineering, the fresh air damper and blower are two separate systems. However, the reality is: the natural wind pressure during driving can introduce at most 10% of fresh air, which fluctuates unpredictably with vehicle speed. Last week while cleaning my AC ducts, I specifically observed that with the blower off, only a faint breeze strong enough to move a strand of hair could be detected at the fresh air intake. Therefore, I recommend developing the habit of coordinated operation - for instance, turning the fan speed knob when activating fresh air mode is far more practical than operating them separately.