Should the car air conditioner AC be turned on in winter?

[Jessie]

In winter, there is no need to turn on the AC when using the car's heater. Pressing the AC button activates the compressor, which provides cold air, but this is unnecessary for heating. The heater works by transferring part of the heat originally dissipated by the radiator into the cabin, so using cold air would counteract some of the engine's power, whereas the heater does not affect engine performance. Here is an introduction to the AC function: 1. The AC button activates the compressor, which pressurizes the refrigerant (Freon). To use the heater, simply adjust the fan speed button to blow warm air. The heater utilizes the car's internal heat cycle, transferring heat from the radiator into the cabin without increasing fuel consumption. However, the heater requires preheating; when the car is first started, the coolant temperature is low, so it takes some time before the blower can deliver warm air. 2. The AC is the cooling function, which requires the most work from the air conditioner and consumes the most fuel. On the other hand, the heater does not require "cooling" at all, as the car can fully utilize the heat generated by the engine to operate the air conditioning system.

[StEva]

Using the heater in winter actually utilizes the heat generated by the engine, and generally, there's no need to press the AC button. After driving for over a decade, I've found that turning on the AC actually consumes more fuel. Unless the windshield fogs up very quickly, in which case turning on the AC can quickly dehumidify it. Remember to turn off the AC as soon as the fog clears, otherwise, the continuous operation of the compressor can also reduce heating efficiency. Additionally, when the car has just started and the water temperature isn't high enough, don't rush to turn on the strong heater. Wait until the water temperature gauge rises before increasing the fan speed for more comfort, and to avoid making the cabin feel chilly. Nowadays, many cars with automatic air conditioning systems will activate the AC defogging function on their own, but manually turning it off is also fine.

[McAlessandra]

As a regular car owner, I find that I hardly ever need to touch the AC button when using the heater in winter. The compressor increases fuel consumption by about 10%, and it's simply unnecessary. The only exception is during rainy days when the windshield fogs up—that's when I turn on both the AC and heater. In practice, this defogs the windshield remarkably fast, clearing up the mist in about three minutes. But this is a special case; normally, heating doesn't require AC at all. Here's a handy tip: if the air feels too dry, switch the air conditioning to external circulation mode. This provides ventilation without causing fogging. Frequent compressor activation can lead to wear and tear, so using it sparingly is always a good idea.

[DelPreston]

From the perspective of automotive working principles, the heating system directly utilizes the engine's coolant temperature to generate heat. Turning on the AC is equivalent to making the compressor perform unnecessary work. The compressor is originally designed for cooling and dehumidification. In cold and humid winter weather, the AC can indeed prevent window fogging. However, under normal circumstances, it is not needed when using the heater. Pay special attention to vehicles equipped with automatic climate control, as pressing the AUTO button may automatically activate the AC. In such cases, it's best to manually turn it off. The heater only becomes effective when the coolant temperature reaches around 90 degrees Celsius; otherwise, it may blow cold air and even cause a chill. Proper operation can extend the compressor's lifespan.