1998 GMC Suburban Owner's Manual - Page 167

Rear Heater (Without Rear Air Conditioning) (If Equipped) _ I Rear Air Conditioningand Rear Heater (If Equipped) If your vehicle has the rear air conditjoning and rear heater system combination. controls are provided to regulate speed of the airflow, location and temperature. If you have a rear heater (without rear air conditioning), the control switch is located on the instrument panel. To increase and decrease the flow of heated air to the rear floor vents, move the switch marked REAR HEAT to the blower speed you want. The knob has three speed positions. To increase the flow of heated air, move the switch toward HIGH. To decrease the flow of heated air. move it toward LOW. To turn the fan off',111ove the switch to OFF. To adjust the airflow speed, turn the fan control knob on the left side of the control panel to the desired blower setting. To activate the rear control, move the fan knob on the front control to REAR CNTL. To regulate the airflow location, adjust the center knob on the control panel. Turn the knob to the right for fluor vent airtlow or to the left for headliner vent airflow. 3-5