Defrost 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 Defrost is selected, air is delivered to the windshield outlets. Vacuum is applied to the mode actuator through the Green vacuum line, and to the defrost actuator through the Red vacuum line. The mode actuator will retract, closing the vent door. The defroster actuator will retract, opening the defroster door and close the heater door through mechanical linkage.