Heat only blowing through dash, checked actuators, what now?

Hey guys,

This is on a 2002 Chevy Blazer.
The air gets heated/cooled fine; blower intensity is fine.

The actuator behind the glove box is moving the white plastic arm and the actuator near the gas pedal is also moving the white plastic arm there, so I think the vacuum is ok.  What else is involved in controlling where the air blows?

I can hear a small noise when the actuator behind the glove box moves the white plastic arm past the middle point, like plastic shifting against plastic followed by a very light pop, but then it continues on its path...is this normal?

Thanks a bunch in advance!