2000 GMC Yukon Owner's Manual - Page 173

Air conditioning will be automatically disabled when the outside temperature drops below a level which air conditioning is ineffective. Remember that in order for the automatic system to perform well, it needs A/C to provide cooling performance. To increase and decrease the flow of cooled air to the rear vents, turn the rotary knob to the blower speed you want. The knob has three speed positions. To increase the flow of cooled air, turn the switch toward 3. To decrease the flow of cooled air, turn it toward 1. To turn the fan off, turn the knob to OFF. To operate the rear system using the front control, just turn the knob to the blower position you want. Rear Air Conditioning and Heating Systems (If Equipped) If your vehicle has one of these systems, you can increase and decrease the airflow at the rear vents. Depending on the system you have and the setting selected, you can send cooled or heated air to the rear of the vehicle. Rear Air Conditioning (Without Rear Heater) (If Equipped) To use the rear control, first turn the front control knob to REAR. Then, the rear control can be used to increase and decrease the airflow. 3-8