Where does the actual “cooling” in an air conditioner occur? It happens along the surface and fins of the evaporator coil, located in the indoor cabinet of the air conditioner—which is also known as the (surprise) evaporator. Warm air drawn through the return air ducts by a blower fan passed over the coil, and the cold refrigerant moving through the coil evaporates. This draws heat from the air (as well as moisture), lowering the temperature of the air. The air continues into the ventilation system and then to the various rooms around the house.
It’s important for an the evaporator coil and fins to have a clean surface. During regular air conditioning maintenance, HVAC technicians always make a check of the coil and fins to see if they are developing dirt and grime across their surfaces. If they are, the technicians clean off the dirt so the air conditioner will work at its best during the summer.