GMC 1994 Yukon Owner's Manual page 144

When you first turn on your vehicle's air conditioning, open the windows to
clear the vehicle of hot air. Using the MAX button can also help. See
"MAX Button" in this section for more information.
Function Display
Your system has a lighted display showing each system when it is operating.
During normal operation, all the lights won't comc o n at thc same time.
Only the ones displaying the current settings will light.
Temperature Selector Bar
The bar under your system display lets you select the temperature of the air
flowing into the passenger area of your vehicle. Press COLD for cooler air
and press HOT for warmer air. Release the bar when the system reaches the
temperature you want. The temperature is shown on the display by the
arrow moving between C and H.
Air Controls (BLEND)
The two buttons to the right of the system display control the air flow. You
can blend the air flow to suit your needs. The amount of blending is shown
on the display by an arrow moving between the figure's feet (floor air flow)
and head (vent air flow).
Left Button
Vent (Top)
:
Press the top of this button and the air flow will come through
the instrument panel vents.
Heater (Bottom)
:
Press the bottom of this button and the air flow will
come through the floor outlet.
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