Chevrolet 1998 Express Van Owner's Manual page 140

Rear Air Conditioning and Rear Heater
If your vehicle has a rear air conditioning and rear heater
system combination, controls are provided to regulate the
temperature, location and speed of the airflow.
Front Passenger Control
To adjust the air temperature, turn the temperature knob
on the right side of the control panel.
For warmer air, turn the knob toward the red area, and
for cooler air, turn the knob toward the blue area.
To regulate the airflow location, adjust the center knob
on the control panel. Turn the knob to the left for floor
vent airflow or to the right 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 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.
Rear Passenger Control
The rear control works just like the front control. It will
allow second seat passengers
to
adjust the controls as
they desire.