GMC 1997 Suburban Owner's Manual page 155

Rear Heater (Without Rear
( I f Equipped)
Air Conditioning)
If you have a rear
heater (without rear air
conditioning), the control
switch is located on the
instrument panel.
To use the rear control, first turn the front control knob
to
REAR CNTL. Then, the rear control can be used to
increase and decrease the airflow.
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, move the switch to OFF.
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