Manual A/C-Heater Systems: Operation: Evaporator

The evaporator cools and dehumidifies the air before it enters the passenger compartment. Heat in the air passing through the evaporator core is lost to the cooler surface of the core, thereby cooling and conditioning the air. As the air loses its heat to the evaporator core surface, any moisture (humidity) in the air condenses on the outside surface of the evaporator core and is drained off as water.