Do you need to turn on the AC when using the car's cold air?

[MacTucker]

You need to turn on the AC when using the car's cold air; otherwise, the air conditioning system will only blow air at normal temperature. This is because the AC button controls the compressor, which is the main component of the cooling system. Keeping the air conditioning at a low temperature for a long time can create a large temperature difference between the inside and outside of the car, which may make you feel uncomfortable or even sick, and it will also increase fuel consumption. If you use the air conditioning for an extended period, it's advisable to open the windows to ensure good air quality inside the car. Additionally, before turning off the engine, you should turn off the air conditioning first to protect the compressor. While you need to turn on the AC for cold air, it's unnecessary to press the AC switch when using warm air, as the warm air simply transfers some of the heat originally dissipated by the radiator into the cabin.

[DelWyatt]

To understand this, we need to start with the principles. The AC button in a car's air conditioning system is essentially the switch that controls the compressor, which is specifically responsible for cooling. So, should you turn it on when you want cold air? In most cases, yes, but it's not absolute. For example, during spring and autumn when the temperature is a cool 20 degrees Celsius, just opening the windows and turning on the fan for natural air can be quite comfortable—turning on the AC in this scenario would only waste fuel. On rainy days when the windshield fogs up, turning on the AC for cooling can quickly dehumidify the air, which is much more efficient than using hot air to defog. From my own decade of driving experience, I've found that after a car has been baking in the summer sun and the interior temperature reaches 40 degrees, you should first open the windows to ventilate before turning on the AC—this way, the car cools down faster.

[LaMolly]

From the perspective of driving comfort, using the air conditioning (AC) can be divided into two scenarios based on needs. First, to cool down the car quickly, the AC must be turned on, especially during the hottest summer days when entering a scorching hot cabin. Without the compressor running, the fan alone would just blow hot air. Second, for minor temperature adjustments, manual air conditioning systems allow you to turn the temperature knob to the blue zone and then turn off the AC, relying on natural airflow for cooling, which also saves fuel. I personally pay close attention to my car's fuel consumption—turning off the AC and opening windows on the highway actually increases drag and consumes more fuel. Meanwhile, idling with the AC on while parked can burn an extra 1-2 liters of gasoline per hour. Additionally, it's worth noting that some older cars may experience reduced power when the AC is on, and turning it off can indeed make acceleration feel more responsive.

[DominicMarie]

It depends on the vehicle's age. With newer models featuring automatic climate control, the compressor activates automatically when you press the AUTO button. My five-year-old SUV works exactly like this - the compressor kicks in when lowering temperatures and stops when reaching the set point, without needing to touch the AC button at all. However, older manual AC systems are different. I remember my first drive in my father's vintage Jetta - turning the knob to maximum cold still blew hot air until I realized the snowflake-patterned button on the dashboard wasn't pressed. Compressors left inactive for a decade can develop Freon leaks, so I recommend running the AC for at least a few minutes monthly, including 2-3 minutes during winter for system maintenance.

[OLucia]

The specific operation depends on the situation. During the southern rainy season, the air is so humid it feels like water can be wrung out. Turning on the AC for cooling can simultaneously dehumidify, making it more comfortable than using the cooling mode alone. I experienced this last year in Xiamen—even with the AC set to 22°C, it still felt sticky. But after running the AC for half an hour, the car interior became much drier. However, in dry and hot regions like Qinghai and Gansu, opening the windows at night is cool enough and saves you from the compressor's buzzing noise. What worries me most is beginners making mistakes: some car models automatically activate the compressor when defogging the windshield. If they see the AC light on and deliberately turn it off, the defogging process slows down even more.

[DiJasmine]

Let's compare several common scenarios: On scorching days with temperatures above 35°C inside the car, AC must be turned on; During rainy days, prioritize AC for defogging; On cool days, turn off AC and use ventilation to save fuel; For long-distance driving, intermittently switch AC on/off to prevent fatigue. My neighbor learned this the hard way last month - thinking the fan alone would suffice during a beach trip with kids, only to have a child vomit from heat in the backseat. Later consultation with the 4S store revealed that even in LO mode, the auto AC compressor still operates. However, EV owners should note: While cooling consumes less power than heating, AC usage still reduces range - my BYD Han's range drops to about 80% when using cooling.