Should the AC switch be turned on for heating?

[StJaxon]

Heating does not require turning on the AC switch. The method and precautions for turning on the heating are as follows: Method for turning on the heating: After starting the car, wait for about 5-10 minutes until the water temperature rises to the normal level. At this point, you can turn on the car's heating. Adjust the air conditioning circulation mode to internal circulation. After switching to internal circulation, the temperature inside the car will gradually rise. Then, switch to the heating mode and press the button with the red arrow. The more times you press it, the higher the temperature inside the car will be. Precautions for turning on the heating: Do not turn on the car's air conditioning because the heating utilizes the car's own heat cycle to save energy. Turning on the AC will increase the car's fuel consumption and reduce its power.

[Billy]

You really don't need to press the AC button specifically for heating in winter. The AC controls the compressor for cooling, while the engine's own heat is sufficient to warm up the cabin. Every time I drive in cold weather, I just turn the temperature knob to the red zone and turn on the fan, and the air from the dashboard becomes warm in two or three minutes. If the windshield fogs up, you can turn on the AC for dehumidification. However, cars with automatic air conditioning will determine whether to start the compressor when you press the auto button, which is particularly hassle-free.

[PenelopeRose]

When using the heating system, the AC is basically unnecessary. The car's heating actually relies on the engine coolant for warmth, and the heating time is similar to the engine temperature gauge rising. Turning on the compressor only increases fuel consumption and adds extra load on the engine. I learned this the hard way last year when I used the AC for temperature control, resulting in fuel consumption soaring to 12 liters. Remember the key difference: the red temperature bar means heating, while the blue temperature bar requires the AC for cooling. However, you can use the AC to quickly remove condensation when defrosting the windshield.

[ErinAnn]

No need to turn on the AC button. The heat for the heater comes directly from the engine compartment's cooling system, and the compressor is only responsible for the refrigeration cycle. The correct operation is to start the engine, wait until the temperature gauge starts moving, then turn on the fan and select the foot or windshield defrost mode. If there's a snowflake icon on the air conditioning control panel of an older car, don't touch it. Back when I drove the company's old Jetta, the mechanic specifically mentioned that running the compressor for heating not only wastes fuel but also risks burning out components.

[LeJosiah]

No need to turn on the AC at all. Simply put, the coolant in the engine compartment accumulates heat in the cooling system, and the air blown through the heater core by the fan provides free heating. I've personally tested this on two cars: an 08 Corolla and a 19 Lavida. After warming up the car, turning off the AC and setting the heater to 25°C, the temperature in the driver's seat can rise by 10 degrees in five minutes. The compressor noise is particularly noticeable and consumes extra fuel. Unless you need to defog the windows for dehumidification, don't touch that snowflake button.

[LeEmma]

Turning on the heater does not require activating the AC. The car's heating system essentially recycles waste heat from the engine, whereas the compressor consumes additional power. The key is to check the temperature setting on the dashboard—just turn it to the red zone. The manual for my SUV specifically states: Using AC in heating mode increases fuel consumption by about 15%. However, there's one special scenario to remember: When using the external air circulation mode, high humidity may cause window fogging—this is the only time you need to turn on the AC with the dehumidification function to quickly restore visibility.