Evaporator Core: Description and Operation

The evaporator coil is located in the heater-A/C housing, on the passenger side of the vehicle. The evaporator coil is positioned in the heater-A/C housing so that all air that enters the housing must pass over the fins of the evaporator before it is distributed through the system ducts and outlets. However, air passing over the evaporator coil fins will only be conditioned when the compressor is engaged and circulating refrigerant through the evaporator coil tubes.

The evaporator coil cannot be repaired and, if faulty or damaged, it must be replaced.

Refrigerant enters the evaporator from the expansion valve as a low-temperature, low-pressure mixture of liquid and gas. As air flows over the fins of the evaporator, the humidity in the air condenses on the fins, and the heat from the air is absorbed by the refrigerant. Heat absorption causes the refrigerant to boil and vaporize. The refrigerant becomes a low-pressure gas before it leaves the evaporator.