2002 GMC Yukon Owner's Manual - Page 186

When both the fan control and mode knobs are in the AUTO position, the system will then automatically maintain the desired cabin temperature as selected. Manual control of functions is also available. Temperature Knob The middle knob on the control panel lets you select the desired air temperature in your vehicle. This knob will allow you to adjust the interior air temperature independent of the function knob setting. Move the knob clockwise toward 82_F (28_C) for warmer air. Move the knob counterclockwise toward 66_F (19_C) for cooler air. When the system is set for automatic operation, sensors will control the fan speed. Full Hot: If you turn the temperature knob past 82_F (28_C), the system will go into the "full hot" mode. The system will remain at that maximum heating setting and the fan will blow at the speed the fan knob is set to. If the fan is in AUTO, it will run at full speed. Full Cold: If you turn the temperature knob past 66_F (19_C), the system will go into the "full cold" mode. The system will remain at that maximum cooling setting and the fan will blow at the speed the fan knob is set to. If the fan is in AUTO, it will run at full speed. Mode Knob -- Manual Operation The right knob on the control panel allows you to choose the direction of air delivery. You can choose to set the climate control system yourself, or let the system work for you by placing the system in AUTO mode. See "Mode Knob -- Automatic Operation" later in this section. (Vent): This setting directs most of the air through the instrument panel outlets and a small amount through the floor outlets. (Bi-Level): Air is delivered through the floor outlets as well as the instrument panel outlets. (Floor): This setting directs most of the warmed air through the floor outlets and some air through the windshield defroster outlets. (Blend): Airflow is divided equally between the floor outlet and the windshield defroster outlets. The air conditioning compressor may run to dehumidify the air to prevent window fogging. 3-6