1995 GMC Yukon Owner's Manual - Page 165

To operate the rear air conditioning system, front air conditioning the system must be on.With the front air conditioningsystem off, the rear system controls can be used to circulate airin the rear of the vehicle. To operate therear system using the front control, just turn the knob to the blower position you want. To use the rear control, firstturn the front controlknob to REAR CNTL. Then, the rear control can be used to increase and flow. decrease the air Rear Heater (Without Rear Air Conditioning) If you have a rear heater (without rear air conditioning), the control switch is located on the instrument panel. 3-5