Chevrolet 1996 Tahoe Owner's Manual page 136

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.
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.
Rear Air Conditioning and Rear Heater
If your vehicle has the rear air conditioning and rear
heater system combination, controls are provided to
regulate temperature, location and speed of the airflow.
To adjust the air temperature, turn the temperature knob
on the right of the control panel.
For warmer air, turn the knob clockwise toward the red,
and for cooler air, turn the knob counterclockwise.
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