What do heat exchange station A and m represent respectively?

A: Automatically determine whether internal circulation or external circulation is needed based on the air quality outside the car. It is automatically detected by sensors and can generally be used in hazy weather. M: Inner loop. That is, manual control cycle mode.

The external circulation mainly plays the role of ventilation, so when the air in the car is dirty, this function needs to be turned on. When driving at high speed, if the car is sealed and only internal circulation is used, it is easy to cause insufficient oxygen in the car, which will cause the driver to drive fatigued and unable to concentrate, posing dangerous risks. Therefore, external circulation should be turned on as much as possible when driving at high speeds or long distances. Internal circulation means that the wind blown by the blower only circulates inside the car. Since no external air is involved, it has the advantages of fuel saving and fast cooling (heating). The disadvantage is that it is not conducive to the renewal of air in the car. External circulation means that the blower sucks air from outside the car and blows it into the car. The advantage is to keep the air fresh in the car, but it consumes fuel and has slow cooling (heating) speed. The difference between internal circulation and external circulation is just to close the air intake airway. Simply put, it is like blowing a fan in a room with the door closed, because the airflow is circulated in a closed environment (95% of cars Air + 5% air leaked from door cracks, etc.), the exhaust gas exhaled by people will be inhaled again, so this is actually an unhealthy way of ventilation. But under certain special conditions, we have to turn on this option, such as driving in a basement or walking in the sand, where the outside air is dirty. It is necessary to turn on the internal circulation, but in time the outside air is always bad. It is also necessary to switch the circulation mode at intervals to inject fresh air into the cabin.