GMC 1996 Savana Van Owner's Manual page 122

To regulate the airflow location, adjust the center knob
on the control panel. Turn the knob counterclockwise
for floor vent air flow or clockwise for headliner vent air
flow. Generally, the upper vents are used for air
conditioning and the floor vents for heating. The control
knob can be set to any blend setting.
To adjust the air flow 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.
The rear control works just like the
front
control. It will
allow second seat passengers to adjust the controls
as
they desire.
3-6