Operation CHARM
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Chevy Truck
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1999
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K 1500 Truck 4WD V6-4.3L VIN W
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Repair and Diagnosis
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Heating and Air Conditioning
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Description and Operation
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Heating and Ventilation
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Modes Description
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Upper Mode
Upper Mode
With the mode knob in the Upper position, the vent valve opens so air can flow to the instrument panel outlet ducts.