Evaporator Core: Description and Operation

Fig.7 Evaporator:

A/C EVAPORATOR
The evaporator is located in the heater-A/C unit housing, under the instrument panel. The evaporator 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 fins will only be conditioned when the compressor is engaged and circulating refrigerant through the evaporator tubes.

The heater-A/C unit housing must be removed from the vehicle to access the evaporator for service. The evaporator cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

Refrigerant enters the evaporator from the variable orifice valve as a low-temperature, low-pressure liquid. 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 when it leaves the evaporator.