If you set your air conditioner to "cool" mode and not "fan" mode, the AC system will engage the cooling components to lower the temperature inside the car. When the AC is set to "cool," the following process takes place:
Compressor Activation: The AC compressor, which is driven by the engine's belt, starts running. The compressor's main function is to compress the refrigerant gas, raising its temperature and pressure.
Condenser Operation: The high-pressure, high-temperature refrigerant gas flows to the condenser, located at the front of the car. The condenser dissipates heat from the refrigerant, causing it to condense into a high-pressure liquid.
Expansion Valve: The high-pressure liquid refrigerant passes through the expansion valve, which reduces its pressure and converts it into a low-pressure, low-temperature liquid.
Evaporator Cooling: The low-pressure liquid refrigerant then enters the evaporator, located inside the car's cabin. As air from the cabin is blown over the evaporator's coils, heat is absorbed from the air, causing the refrigerant to evaporate into a gas again.
Blower Motor Operation: The blower motor, also known as the fan, pushes the now cooled air over the evaporator coils back into the cabin, providing you with cold air.
Recirculation/Outside Air: Depending on your car's settings, the AC system may use recirculated cabin air or draw in outside air, which is then cooled and recirculated into the cabin.
If you set the AC to "fan" mode instead of "cool," the cooling components like the compressor and evaporator won't be activated. Instead, only the blower motor will run, circulating the existing air inside the car without any cooling effect. The air blown into the cabin will be at the ambient temperature, and you won't experience any cooling effect.
It's important to set your AC to "cool" mode when you want to lower the temperature inside your car. Setting it to "fan" mode is useful when you only want to circulate air without cooling, such as on a mild day or when you're trying to ventilate the cabin without using the AC.