2008 GMC Sierra 1500 Pickup Owner's Manual - Page 161

Temperature Control: Turn the center knob clockwise or counterclockwise to increase or decrease the temperature inside the vehicle. Use the right knob to select from the following modes: The right knob can be positioned between two modes to select a combination of those two modes. Defogging and Defrosting Fog or frost on the inside of windows is a result of high humidity (moisture) condensing on the cool window glass. This can be minimized if the climate control system is used properly. Turn the right knob to select the defog or defrost mode. H (Vent): This mode directs air to the instrument panel outlets. - (Defog): ) (Bi-Level): 6 (Floor): This mode directs half of the air to the instrument panel outlets and to the floor outlets. This mode directs most of the air to the floor outlets with some air directed to the windshield, side window outlets, and second row floor outlets. In this mode, the system will automatically select outside air. This mode clears the windows of fog or moisture and warm the passengers. The air is directed to the windshield, floor outlets, and side window vents. This mode removes fog or frost from the windshield more quickly. A portion of the air is directed to the windshield and the side window vents, with some air directed to the floor vents. The system will automatically force outside air into the vehicle. Do not drive the vehicle until all the windows are clear. 0 (Defrost): 3-25