GM Service Manual Online
For 1990-2009 cars only
Ventilation Mode: In the ventilation mode, air is discharged from the upper air outlet.

Bi-Level Mode: In the bi-level mode, airflow is divided between the upper air outlets and the floor air outlets, with warmer air delivered to the floor outlets than is delivered to the upper air outlets.

Heat Mode: In the heat mode, air is directed to the floor outlet, along with a small amount of air to the windshield.

Heat/Defroster Mode: In the heat/defroster mode, a portion of the heated air is routed to the windshield. The remaining air is delivered to the floor and the side window outlets.

Defrost Mode: In the defrost mode, most of the air is directed to the windshield. A small amount of air is delivered to the side windows and to the floor.