Chevrolet 2004 Express Van Owner's Manual page 144

To change the current mode, select one of the following:
D
(Vent): Use this mode to direct air to the upper
outlets, with a little air directed to the floor outlets.
2
(Floor): Use this mode to direct most of the air to
the floor outlets.
9
(Fan): Turn the left knob clockwise or
counterclockwise to HIGH, MED (Medium) or LOW to
increase or decrease the fan speed in the rear-seating
area. Turn the knob to OFF to turn off the fan.
3-24
(Temperature Control): To increase or decrease the
temperature for the rear of the vehicle, turn the right
knob located on the climate-control panel.
The air-conditioning system on the main climate-control
panel must be turned on to direct cooled air to the
rear of the vehicle. If it is not on, then the temperature
in the rear of the vehicle will remain at cabin
temperature.
Be sure to keep the area under the front seats clear of
any objects so that the air inside of your vehicle can
circulate effectively.
For information on how to use the main climate-control
system, see Climate Control System on page 3-19
listed previously in this section. For information
on ventilation, see "Outlet Adjustment" earlier in this
section.