A/C Heater Blower flap/actuator problem - 2000 P11

I have a 2000 G20 and the A/C only blows out the windshield vents. The mode button works fine and it switches between feet (floor vents), face (dash vents), and windshield vents but regardless of setting the air only blows out of the windshield vents (defroster mode). I assume it is an issue with the flap motor/actuator. I found two actuators under the dash, one on the side and one under the center dash near the floor. Can anyone shed any light on which actuator controls the air flow to the vents and it's location? Could the problem be something else? Thanks.