Chevrolet 2007 Colorado Owner's Manual page 179

Recirculation is only available in the bi-level and
vent modes. It should only be used while in bi-level
and vent modes. Recirculation is not available,
and the light will not come on or flash while in heat,
floor, floor/defog, or defrost modes.
#
(Air Conditioning): Press this button to turn
the air conditioning system on or off. An indicator
light on the button will come on to let you know
the air conditioning is activated. When the system
is on, this setting cools and dehumidifies the
air entering your vehicle.
The air conditioning will not function if the fan is
turned off.
You may notice a slight change in engine
performance when the air conditioning compressor
shuts off and turns on again. This is normal.
The system is designed to make adjustments to
help with fuel economy while still maintaining
the selected temperature.
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 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 and side windows. Use the defog
mode to clear the windows of fog or moisture and
warm the passengers. Use the defrost mode to
remove fog or frost from the windshield more
quickly. For best results, clear all snow and
ice from the windshield before defrosting.
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