Vent Mode
WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
When VENT is selected, air is delivered through the instrument panel outlets with a small amount of air delivered to the floor. Vacuum is applied to the mode actuator through the Violet vacuum line, and to the defrost actuator through the Yellow vacuum line. The mode actuator will retract, opening the vent door. The defroster actuator will retract, closing the defroster door and open the heater door through mechanical linkage.