Should the AC be turned on when using the car's heater?
2 Answers
When using the car's heater, there is no need to turn on the AC because the heating system in a car does not require the compressor to work for heating. Instead, it directly utilizes the heat from the engine's cooling system as warm air. Therefore, during winter when using the heater, there is no need to activate the AC switch. However, it is important not to keep the car windows closed for extended periods when using the heater in winter, as the engine produces harmful gases such as carbon monoxide. Hence, it is necessary to remember to ventilate the car's interior when using the heater in winter. The car's air conditioning system also features other functions like internal circulation, external circulation, and air supply mode, which should be used according to different situations. For example, when the external air quality is good, the external circulation mode can be used to refresh the air inside the car, while the internal circulation mode is suitable for the opposite scenario.
After driving for so many years, I've found that when using the heater in winter, there's no need to press the AC button at all—because that little button controls the air conditioning compressor, mainly used for cooling or dehumidifying. The car's warm air actually comes from the engine's waste heat. The engine coolant flows through the heater core, and the fan blows out warm air without any need for the compressor. If you turn on the AC, the compressor will start working, wasting fuel unnecessarily and even making the air inside the car drier and less comfortable. Only in particularly damp and cold weather, such as snowy or rainy days when the windows fog up easily or the interior gets too humid, do I turn on the AC for dehumidification: this way, the warm air blown out is both cozy and dry, keeping the windshield clear and safer. I make it a habit to turn the temperature knob to the high zone without AC as soon as I get in the car—it saves fuel and hassle. I still remember the last time I forgot to turn off the AC on the highway, and my fuel consumption increased by 5%. Now, I always check the button position before driving to ensure comfort and economy. In short, most of the time, don't use it—it's just there as a backup for dehumidification.
