2007 GMC Sierra 1500 Pickup Owner's Manual - Page 231

W (Defog): Airflow is delivered through the floor outlets, the windshield defroster outlets, and the side window defroster outlets. The air flow can be divided between floor and defrost depending upon where the knob is placed between the settings. Dual Climate Control System With this system you can control the heating, cooling, and ventilation for your vehicle. 1 (Defrost): This setting directs most air through the windshield defroster outlets, side window defroster outlets, and some through the floor outlets. Fan Control 9 (Fan): Turn the left knob clockwise or counterclockwise to increase or decrease the fan speed. Turn the knob to the off position to turn off the fan. If the knob is in off, outside air will still enter the vehicle and will be directed based on the position of the mode knob. The temperature can also be adjusted using the temperature levers. Turn the right knob clockwise or counterclockwise to direct the airflow inside of your vehicle. 231