379 a/c duct problem

Hello all,

Here is my problem.

A/C is charged, blower motor seems to be working ok. When i have the vent setting on dash face vents, there is barely any air flow. When i switch to either heater or defroster vents, there is good air flow. When i switch back, barely any air, but the heater and defrost have no air flow (as it should be). Are there multiple doors in the duct work that control the flow, rather than just one, like most vehicles have? Thank you in advance for any helpful suggestions.

 

2004. I believe they are electric.

 

Not replaced, but removed and cleaned often

 

Any idea on how i get to them to check/replace?