2001 GMC Sierra 1500 Pickup Owner's Manual - Page 196

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) 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 select the fan speed. Rear Control Front Control To increase and decrease the flow of cooled air to the rear vents, turn the rotary knob to the fan speed you want. 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. 3-9