Fresh/Recirculated Air Selector
WARNING: This page is about a different car, the 2001 Hyundai Accent and 2000 Hyundai Accent. However, it is still accessible from the selected car via links, so may be relevant.
Fresh/recirculated air selector uses vacuum to select airflow source. With selector at recirculated air setting, vacuum is applied to outside door vacuum motor. Air is then allowed to recirculate and pass through heater core. With selector at fresh air setting, vacuum is applied to outside door vacuum motor and outside air is allowed inside passenger compartment. Recirculated air position is used to achieve maximum heating or while driving on dusty roads.