Do you need to turn on AC when using the heater?

[GabrielleMarie]

You don't need to turn on AC when using the heater. The AC button controls the compressor switch, while the heater mainly utilizes the internal heat circulation of the car to maintain cabin temperature. During this process, the compressor doesn't work - you only need to adjust the airflow. Turning on AC would waste fuel. To use the heater, first start the engine for preheating. When the engine temperature gauge reaches the middle position, turn on the heating system while setting air circulation to external mode to expel cold air from the cabin. After 2-3 minutes, switch to internal circulation. Sleeping in a car with heater on is extremely dangerous. For prolonged heater use, slightly crack open a window to maintain warmth while preventing carbon monoxide poisoning.

[JamesRose]

I recently encountered an issue with using the heater in my car during winter and have been pondering whether to press the AC button. Initially, I always turned it on together, thinking it would warm up the car faster. Later, I learned from fellow car owners that AC actually stands for air conditioning compressor, mainly used for cooling, and isn't necessary when using the heater. The engine's heat is sufficient to warm the air, unless it's humid or raining and the windows fog up—then turning on the AC can help dehumidify. Now, my habit is to adjust only the temperature knob for heat, set the fan to medium, and keep the AC off; I only briefly turn on the AC to defog when needed. This trick has helped me save quite a bit on fuel, since running the AC increases fuel consumption by about 10%. Over time, this can save hundreds of dollars in fuel costs annually and also reduces wear on the compressor. Regular maintenance of the cabin air filter is also crucial to ensure the system remains clean and efficient.

[Mario]

After driving for so many years, I've gained deep insights into operating the heating system - you don't need to turn on the AC for heating at all. Through accumulated experience, I've learned that AC is specifically for cooling, while winter heating primarily utilizes engine-generated warmth delivered through air vents. I only press the AC button for dehumidification when the car interior gets damp or the windshield fogs up, as AC can dry the air and quickly clear condensation. Normally, I simply turn up the temperature dial for heating with moderate fan speed; I promptly turn off AC once defogging is complete to avoid unnecessary fuel consumption. This simple and practical operation can save 5%-10% fuel and extend the air conditioning system's lifespan. I recommend fellow drivers develop the habit of checking AC status before each startup and regularly cleaning filters to maintain smooth operation.

[GriffinDella]

As a car owner who particularly cares about fuel efficiency, there's definitely no need to turn on the AC when using the heater. The AC increases engine load and leads to higher fuel consumption – I've calculated that running the AC all day can cost about half a liter more fuel. The heating system itself utilizes waste heat from the engine, blowing warm air into the cabin through a heat exchanger without relying on the compressor. Only when the interior air is humid, like during rainy or foggy conditions, should the AC be activated to dehumidify and defog for safe visibility. My habit is to run the heater independently with the AC off in dry weather, and briefly turn on the AC as an assist during humid conditions. This practice helps me save fuel and be eco-friendly, with long-term adherence significantly reducing vehicle operating costs. Regularly inspecting and cleaning the vehicle's ventilation system is crucial.