Should the AC be turned on when using the car's air conditioning?

[SanCassidy]

To use the cold air function, you must press the AC button; otherwise, the air conditioning system will only blow air at normal temperature. This is because the AC button controls the compressor, a key component of the cooling system. When using the cold air function, try to avoid prolonged use. Keeping the air conditioning at a low temperature for too long can create a significant temperature difference between the inside and outside of the car and increase fuel consumption. The car's air conditioning cooling system consists of a compressor, condenser, receiver-drier, expansion valve, evaporator, and blower. These components are connected by copper (or aluminum) pipes and high-pressure rubber hoses to form a sealed system. When the cooling system operates, the refrigerant circulates through this sealed system in different states, achieving the purpose of lowering the temperature of the air around the evaporator. Compression process: The compressor draws in low-temperature, low-pressure refrigerant gas from the evaporator outlet and compresses it into high-temperature, high-pressure gas, which is then discharged from the compressor. Heat dissipation process: The high-temperature, high-pressure superheated refrigerant gas enters the condenser. Due to the drop in pressure and temperature, the refrigerant gas condenses into a liquid, releasing a large amount of heat. Throttling process: The higher-temperature and higher-pressure refrigerant liquid passes through the expansion device, where its volume increases, and its pressure and temperature drop sharply, exiting the expansion device as a mist (fine droplets). Heat absorption process: The mist-like refrigerant liquid enters the evaporator. Since the boiling point of the refrigerant is much lower than the temperature inside the evaporator, the refrigerant liquid evaporates into a gas. During this process, it absorbs a large amount of heat from the surroundings, and the low-temperature, low-pressure refrigerant vapor then re-enters the compressor. Precautions for using the air conditioning in the car: Do not set the air conditioning temperature too low. A large temperature difference between the inside and outside of the car can easily cause the driver to catch a cold, and excessively low temperatures may also increase the risk of arthritis for passengers. Control the direction of the air vents. Based on the principle that cold air sinks and hot air rises, when using the air conditioning, set the vents to face upward when cooling and downward when heating. Do not turn on the air conditioning immediately after the car has been exposed to the sun. After prolonged exposure, the temperature inside the car will be very high. First, open the windows to ventilate and allow the hot air to escape before turning on the air conditioning.