Chevrolet 2004 Venture Owner's Manual page 212

These controls are overhead, on the control panel located
behind the driver's seat. A rear seat passenger can use
these controls to personally adjust the temperature and
the fan speed for the rear seating area.
3-30
The fan knob located on the switchbank must be turned
to R (Rear) to allow the rear seat passengers to use
the controls located on the control panel in the rear
seating area. Performing this action disables the
fan knob on the switchbank. To return control to that
knob, turn the knob out of R.
To direct the airflow to the rear seating area, use the
right knob located on the main climate control panel.
•
Select vent or bi-level mode to direct air to the
rear of the vehicle through the overhead outlets.
•
Select floor, defog, or defrost mode to direct air to
the rear of the vehicle through the floor outlets.
Generally the upper outlets are used for air conditioning
and the floor outlets are used for heating.