GMC Envoy Owner's Manual page 165

Envoy XL
To operate the rear air conditioning system, the front air
conditioning system must be on. With the front air
conditioning system off, the rear system controls can
only be used to circulate air in the rear of the vehicle.
To activate the second row seat controls in the following
systems, set the fan knob, located on the front
console, to R.
3-30
To adjust the airflow speed,
turn the fan knob (driver
override switch), located on
the front center floor
console to 1, 2 or 3.
The rear mode and
temperature positions
now mimic the front
control system mode
and passenger
side temperature.
Envoy XL
Turn the knobs on the control panel to choose a fan
speed, temperature and direction of airflow.
H
(Panel): Selecting panel mode will deliver air
to the four headliner outlets.
)
(Bi-level): Selecting bi-level mode will deliver
warmer air to the third seat floor outlet and cooler air
to the headliner outlets.
6
(Floor): Selecting floor mode will deliver air
to the floor outlet located in the third seat area.