AC only comes out lower vents

[Shadowranger]

So, after 3 months in the shop due to parts availability, I finally got the Ranger back yesterday. Engine pulled, main seal, transfer case seal, heads and valves done, on and on.
Now the AC, which worked fine before this, only blows out the lower vents and with less volume than normal, even on high. There's only a slight volume of air at the upper vents and it's barely noticeable.
What could this be from? I've had rats enter both vehicles in the past and I think if a duct was blocked I would have smelled it by now. Any ideas?
2001 XLT, 4.0 4x4 auto.

 

[dvdswan]

they may have forgot to hook up a vacuum line or pinched one. That's if the HVAC needs vacuum to operate.

 

[Shadowranger]

I have to wait until a seal arrives before I go back to the shop and he can look at it.
I hope it's an easy fix because it's getting hotter every day.