Should I turn on the AC switch when the car is heating up?

In most cases, it is not necessary to turn on the AC switch of the air-conditioning compressor to turn on the warm air, but some old drivers operate more advanced, and turn on the air conditioner at the same time as turning on the warm air. Let's explain the specific reasons in detail. There is a device under the center console of the air-conditioning heater car, which we will call "temperature control box" for the time being. One end is connected with the air conditioning filter element, and the other end is connected with the air outlet inside the vehicle. There are many things in the temperature control box, such as evaporation box, warm air box, mixing damper, fan and so on. Needless to say, the function of the fan is to blow and drive the airflow. The evaporation box is connected with the compressor of the air conditioner, and the refrigerant compressed by the compressor evaporates and absorbs heat in the evaporation box to cool the air, which is the source of cold air of the air conditioner in summer. The heater box is equivalent to a small radiator, connected to the engine cooling system, and the coolant flows in it. Why doesn't the water temperature come up in winter and the warm air is not hot? That's because the coolant temperature is low. The hybrid damper is a baffle. If the airflow path changes, it can mix hot and cold air to adjust the outlet temperature. The figure shows the working principle of the hybrid damper. The thing that opens and closes back and forth in the picture is the mixing damper. This is a touching film. I set the screen switching time to 10 second to make it easier for people to find words. The picture above shows the structure of a simulated thermostat. After the fan drives the airflow into the thermostat, the airflow first passes through the air conditioner evaporator and then through the warm air water tank. Red represents the mixing damper. The mixing damper can be rotated to change the airflow path. For example, the above picture shows the state when the warm air is turned on, the air door is opened, and the air flow passes through the evaporator and then through the warm air box. If the engine water temperature is normal at this time, the air flow will be heated by the heater box and the hot air will be blown out of the car. At this time, if the AC switch is turned on, the evaporator will produce low temperature. Initially, 10 degrees Celsius air enters. When you turn on the air conditioner switch, the temperature will drop to 5 degrees Celsius. At this time, the heating water tank will lose more heat to heat the air, and the outlet water temperature will inevitably decrease. So if you turn on the warm air to keep warm, there is absolutely no need to turn on the AC switch. This not only wastes engine power, but also increases the heat loss of engine coolant. When the air conditioner is turned on, the air conditioner switch is turned on, the compressor is started, and the evaporator produces low temperature. At this time, the mixing damper will block the warm air tank, so that the airflow will enter the thermostat, cool down through the evaporator, bypass the warm air tank and directly enter the cockpit. If the mixing damper does not block the warm air tank, the air flow will be cooled and heated by the warm air tank, which is a waste. Dehumidification mode This is what I call the old driver operation mode, dehumidification mode. When the warm air is turned on, the AC switch of the air conditioner is also turned on, so that the airflow passes through the evaporator first, and the water vapor in the airflow condenses on the evaporator, which reduces the humidity of the airflow and becomes drier. Then the dry air flow is heated by the warm air tank and sent to the cockpit. Why dehumidify? Mainly used for rapid defogging. Because the fog on the windshield is mainly due to the high humidity of the air inside the car, it is best to blow it with warm air at this time, but the premise is that the humidity of the airflow blown by warm air is small. If the humidity is too high, it is no different from blowing on the windshield, but it will aggravate the fog. At this point, turn on the compressor, and use the dehumidification characteristics of the air conditioner to dehumidify the airflow first, and then heat the dry airflow and send it to the cockpit for defogging. The effect will be perfect. So when you say that the effect of warm air defogging is not good, don't hesitate to turn on the AC switch immediately, which may have unexpected effects. Certain automatic air conditioners basically do not need to be operated. Most cars will automatically turn on the AC switch for you after turning on the defogging mode. If your car won't start automatically, you can manually turn the air conditioner to the highest temperature and then turn on the AC button. Manual air conditioning, just turn the thermostat knob to the red area. In this way, the mixing damper in the temperature control box will completely expose the warm air tank. At this time, the intake air will be dehumidified by the evaporator and then heated by the warm air box to become dry and hot air, and the defogging effect will be greatly improved.