[davester]

It could be a bad out of the box actuator, or a wiring problem or the HVAC head unit.

 

[davester]

Sir, thank you for your response. I do believe you nailed it. The blend door I need to get to is on top of the dash below the duct work. Taking the dash off to get it is a bear and very time consuming. Going to attemp to enter and see if I can reach the blend door from where the sterio is and attemp to unplug it and see if I can get it to unlock. I had success doing this on a Honda that was not so buried in the dash. Any tips would be greatly appreciated.

I don't think that's a blend door. Both driver and passenger blend doors are replaceable w/o having to disassemble the dash, just need to remove the cover along the bottom. The mode door also is relatively easy to replace. The one buried in the dash is the recirculation door, which is unlikely to be the source of your problem.

The driver's side blend door actuator is, IIRC, along the front of the dash, just above the hump.
First hit from googling "gmt800 replacing drivers blend door actuator"

 

[davester]

Yes, there is a separate one for the passenger side, close to where the fan is. google for gmt800 passenger blend door actuator replacement.

 

[davester]

And if the passenger side doesn't move, it might be the actuator, or maybe a wiring problem, or maybe the hvac HU.

 

[davester]

IDK, I was able to replace mine, in my '04 3500, w/o needing to disassemble the dash.