Blower Motor: Description and Operation

In any operating mode (except OFF) the blower motor draws in air from the plenum and pushes it through the evaporator. When any air conditioning or defrost mode is selected, the air conditioning refrigeration system chills the core of the evaporator to slightly above freezing temperature. This cools the airflow and causes excess humidity to condense on the fins of the evaporator. The condensed moisture drips to the bottom of the case and drains out through a hole that lets the water fall on the road surface below the vehicle. From the evaporator, the air flows toward the temperature valve and heater core.