Fresh/Recirculated Air Control
WARNING: This page is about a different car, the 1994 Honda Prelude. However, it is still accessible from the selected car via links, so may be relevant.
The position of the fresh/recirculated air door (part of blower unit) determines whether fresh (outside) air or recirculated (inside) air enters the heating system. This door is controlled by an electric recirculation control motor.