GMC 2007 Yukon XL Owner's Manual page 214

Driver's Side Temperature Control
The driver's side temperature buttons are used to
adjust the temperature of the air coming through
the system on the driver's side. The temperature
can be adjusted even if the system is turned
off. This is possible since outside air will always
flow through the system as the vehicle is moving
forward unless it is set to recirculation mode.
See "Recirculation" later in this section.
Press the + or buttons to increase or decrease
the cabin temperature. The driver side
temperature display will show the temperature
setting decreasing or increasing.
214
Passenger's Side Temperature Control
The passenger's temperature buttons can be used
to change the temperature of the air coming
through the system on the passenger's side of the
vehicle. The temperature can be adjusted even
if the system is turned off. This is possible
since outside air will always flow through the
system as the vehicle is moving forward unless it
is set to recirculation mode. See "Recirculation"
later in this section.
Press the + or buttons to increase or decrease
the cabin temperature. The passenger side
display will show the temperature setting
decreasing or increasing.
The passenger's temperature setting can be set to
match the driver's temperature setting by pressing
the PASS button and turning off the PASS indicator.
When the passenger's temperature setting is set
different than the driver's setting, the indicator on
the PASS button will illuminate and both the driver's
side and passenger's side temperature displays will
be shown.