Should the AC be turned on when using the heater?
3 Answers
When using the heater in the car, there is no need to turn on the A/C switch. This is because the warm air is generated by the heat from the car's engine and circulated into the cabin through the air conditioning system, without requiring the compressor to operate. Turning on the A/C not only fails to improve the heating effect but also increases fuel consumption. Correct usage of the A/C button: 1. The A/C button controls the on/off function of the air conditioning compressor. In summer, drivers need to turn on the A/C button along with the cold air setting to activate the cooling function, allowing cold air to circulate inside the car. 2. Drivers can turn off the A/C switch during acceleration or rapid acceleration because the air conditioning compressor is powered by the engine and consumes some of the engine's power. Turning off the A/C switch can prevent insufficient engine power.
When using the heater, you usually don't need to turn on the AC button because the heat comes from the engine coolant. Turning on the AC will only make the compressor run idle and waste fuel. However, there's a little trick for driving in humid southern regions during winter: when you first start the car, the windows are prone to fogging up. At this time, turning on the AC can quickly dehumidify, and you can turn it off once the fog clears. I commute half an hour on the highway every day, and my personal experience shows that turning on the AC for two minutes before switching to the heater in winter keeps the windows fog-free throughout the trip. Also, be careful not to set the temperature too high; around 22 degrees is the most comfortable, otherwise the hot air blowing on your face can make you drowsy.
As a seasoned driver with over a decade of experience, I recommend not using the AC at all when turning on the heater. Think about it—the compressor is for cooling, and using it increases engine load and fuel consumption, which is completely unnecessary. The heater relies on the engine's water temperature, and the best effect is achieved by letting the car idle for five minutes before turning on the heater. Of course, exceptions apply in special cases, such as when the windshield fogs up severely on rainy days. In such situations, you can temporarily turn on the AC for ten minutes for strong dehumidification, which works three times faster than using the heater alone. Another tip: switch to external circulation mode when using the heater to prevent repeated fogging on the windshield—much more efficient than mindlessly running the AC.
