The heating and cooling knob is used to adjust the air outlet temperature, and is set at the warm end (generally red). The air duct is switched to warm air state, heated by hot water in the engine water tank, and set at the cold end (generally blue). When the air duct is switched to the state of air-conditioning evaporation box, cold air will be discharged when the air-conditioning compressor (that is, the air-conditioning button) is turned on. If the air-conditioning compressor is not turned on, it is natural wind (ambient temperature), and the position between the two ends is the temperature adjustment range (the hottest end and the coldest end).
The size of the fan is the wind speed, and the higher the gear, the stronger the wind; Internal and external circulation, internal circulation is to inhale air from the car and then blow it out from the air outlet. The air inlet is usually under the center console. If you want to heat up or cool down quickly, or the air outside smells strong, switch to internal circulation. External circulation means sucking air from the outside and blowing it out from the air outlet. The air intake is generally under the hood, so it can be switched to external circulation at ordinary times to keep the air inside the car fresh.