Defogging And Defrosting; Ventilation System - GMC C series 2002 Owner's Manual

Defogging and Defrosting

Use DEFOG, along with the floor setting, when there is
fog or ice on the windshield. This will direct airflow
toward the windshield and front side windows. Set the
temperature selector toward H and the fan control at a
comfortable level. When the windshield is clear, use the
temperature selector bar and the fan button to maintain
a comfortable temperature level.
3-6

Ventilation System

Air comes into your vehicle in one of two ways: power
air or ram air. Power air means bringing outside air into
the cab through the air intake, using the fan. Outside
air can be drawn in when the vehicle is stationary or
moving at low speed. Air comes in through four vents in
the instrument panel and is exhausted through the vents
and pressure relief valves in the doors and door pillars.
Power ventilation means an increased supply of outside
air is brought into the cab interior without having to
open the windows, especially during inclement weather.
Ram air is forced into the cab through the air intake in
the cowl by the vehicle's forward motion. This air is
controlled by two vent air handles under the instrument
panel. Air is directed through the ventilation ducts to the
floor. Ram air provides good airflow into the cab at
normal road speeds.