Do you need to turn on the AC for car heating?

[LeJohn]

You do not need to turn on the AC for car heating. Below are the working principle of the AC button and precautions for using the car air conditioning: Working principle of the AC button: After turning on the AC button, the electromagnetic clutch of the air conditioning compressor will engage, causing the compressor to operate, and the car air conditioning will enter the cooling mode. Precautions for using car air conditioning: Do not always use the internal circulation mode. Although it helps save fuel, prolonged use can make the air inside the cabin stale and oxygen-deprived. Regularly clean or replace the car air conditioning filter and clean the air ducts to ensure air quality from the air conditioning.

[WalterAnn]

Last time I specifically asked the mechanic, you don’t need to press the AC button to get warm air in winter! Turning on the AC activates the compressor for cooling, while the heat comes from the engine itself. Just like you don’t need to turn on the fridge to get heating at home, the warm air in the car comes from the hot coolant circulating from the engine. Turning on the AC unnecessarily increases fuel consumption, as the compressor keeps running and wastes fuel. Just remember to turn the temperature knob to the red zone, adjust the vents to the right direction, and the car will warm up in minutes. The only time you need to use AC is when the windshield fogs up, but turn it off immediately after defogging to save fuel.

[SanLondon]

A veteran driver with over a decade of experience tells you: The AC button for heating is completely unnecessary! The heating system utilizes waste heat from the engine. Turning on the heater before the engine reaches operating temperature actually slows down the warming process. My car's manual clearly states on page 135: AC is for cooling and dehumidification. While using AC does defog windows faster in cold weather, keeping it on during normal heating consumes 15% more fuel! Here's a fuel-saving tip: Wait until the coolant temperature gauge reaches the midpoint before turning on the heater, use recirculation mode to retain heat, and turn off AC - the fuel savings could buy you breakfast!

[OLucia]

Just studied car AC principles: The AC button controls the compressor, which is completely independent of the heating system. The warm air comes from the heat exchange of engine coolant flowing through the heater core, similar to a hot water bag at home. Turning on AC not only fails to assist heating, but the idling compressor belt actually consumes 2-3 horsepower. Try this test: Compare turning off AC with heat set to 30°C versus turning on AC at 30°C - the latter's vent temperature will be at least 3 degrees lower. New cars with automatic climate control are exceptions, but remember for manual heating control - an illuminated AC light equals a fuel-burning light!

[SawyerRose]

Young drivers should know these practical tips: Shivering in the car and turning on the AC for heat in winter is completely useless! That snowflake icon lit up means the compressor is cooling, working against the warm air you want. The correct operation should be: When the coolant temperature reaches around 90 degrees, turn the temperature knob to the red MAX, set the fan to the second or third gear, and choose the foot + windshield mode. Don't panic when your phone mount can't stick due to the cold, keep a window cleaning cloth handy for emergencies. In the north where temperatures drop below zero, remember to switch to -25-degree windshield washer fluid in advance—frozen spray nozzles are more frustrating than having no heat.

[LeColin]

As a system engineer, I must say: the car's heating circuit design never considered AC involvement. The heating valve directly controls coolant flow, just like adjusting a hot water faucet. The AC evaporator is located in the cold air duct, physically separated from the heating radiator. Forcing both systems to run simultaneously causes thermal cancellation, with the system consuming an additional 0.8L/100km to handle condensation. Test data shows: using AC for heating at 5°C environment consumes 23% more energy than without AC. We recommend users open windows every two hours in winter for air exchange to avoid CO₂ buildup, which is much wiser than relying on AC ventilation.