The aluminum evaporator core cools and dehumidifies the air before the air enters the passenger compartment. High pressure refrigerant liquid flows through the expansion (orifice) tube and becomes low pressure refrigerant liguid before entering the evaporator. As the air passes through the core, the cooler surfaces absorb the heat, cooling the air. As the air is being cooled, any humidity in the air condenses on the outside of the core. The water is then drained through an opening in the module. The evaporator core is located inside of the HVAC module.