GMC Yukon 2007 Owner's Manual page 229

The recirculation mode cannot be used with floor,
defrost, or defogging modes. If you try to select
recirculation in one of those modes, the indicator
will flash three times and turn off. The air
conditioning compressor will also come on when
this mode is activated. While in recirculation mode
the windows may fog when the weather is cold
and damp. To clear the fog, select either the defog
or defrost mode and increase the fan speed.
Recirculation mode can be turned off by pressing
the button again, or turning off the engine.
AUX (Auxiliary): Pressing this button will turn the
rear heating and air conditioning on. See Rear
Air Conditioning and Heating System on page 239
or Rear Air Conditioning and Heating System
and Electronic Climate Controls on page 240 for
more information.
Temperature Control: Rotate the thumbwheels
up or down to increase or decrease the
temperature on the driver's side or the passenger
side of the vehicle for the dual zone system.
#
(Air Conditioning): Press this button on the
left knob to turn the air conditioning system on
or off. When A/C is pressed, an indicator light will
come on to let you know that the air conditioning
has been activated.
On hot days, open the windows to let hot inside
air escape; then close them. This helps to reduce
the time it takes for your vehicle to cool down.
It also helps the system to operate more efficiently.
The air conditioning system removes moisture
from the air, so you may sometimes notice a small
amount of water dripping underneath your
vehicle while idling or after turning off the engine.
This is normal.
Defogging and Defrosting
Fog on the inside of the windows is a result of
high humidity (moisture) condensing on the
cool window glass. This can be minimized if the
climate control system is used properly. There are
two modes to clear fog or frost from your
windshield. Turn the right knob clockwise to select
the defog or defrost mode.
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