GMC Yukon Denali 2006 Manual page 168

If the driver's and passenger's temperature settings
are not the same, the opposite side temperature
setting will be displayed for an additional
five seconds. To make the passenger's temperature
the same as the driver's press and hold the
AUTO button for about four seconds.
When auto is selected, the air conditioning operation
and air inlet will be automatically controlled. The
air conditioning compressor will run when the
outside temperature is over about 40°F (4°C). The
air inlet will normally be set to outside air. If it's
hot outside, the air inlet may automatically switch to
recirculate inside air to help quickly cool down
your vehicle. The light on the button will illuminate
in recirculation.
2. Set the driver's and passenger's temperature.
To find your comfort setting, start with a 74°F (23°C)
temperature setting and allow about 20 minutes
for the system to regulate. Turn the driver's or
passenger's side temperature knob to adjust the
temperature setting as necessary. If you choose the
temperature setting of 60°F (15°C) the system
will remain at the maximum cooling setting. If you
choose the temperature setting of 90°F (32°C)
the system will remain at the maximum heat setting.
Choosing either maximum setting will not cause
the vehicle to heat or cool any faster.
3-22
Be careful not to cover the sensor located on the
top of the instrument panel near the windshield.
This sensor regulates air temperature based on sun
load, and also turns on your headlamps.
To avoid blowing cold air in cold weather, the
system will delay turning on the fan until warm air is
available. The length of delay depends on the
engine coolant temperature. Pressing the fan switch
will override this delay and change the fan to a
selected speed.
9 (Off): Press this button to turn off the entire climate
control system. Outside air will still enter the vehicle,
and will be directed to the floor. This direction can
be changed by pressing the mode button. The
temperature can also be adjusted using either
temperature knob. Press the up or down arrows on the
fan switch, the defrost button, the AUTO button, or
the air conditioning button to turn the system on when
it is off.