Get your freon checked to make sure your system is charged.
I had a similar problem,i.e., warm air out of the passenger side, and thought it was the blend door. Got it charged and everything was okay.
To check that it wasn't the blend door, i did the following,
1) remove you glovebox
2)turn the car on
3)while looking at the left inside part in where the glovebox was, turn the ac from cold to hot or vice versa, you should see one of the white circle things turning. If you dont see one turn, then your blend door motor is bad.
4)If you see one move, you can actually cut into the plastic with a razor blade couple inches above it, with a hole large enough to stick your finger through to feel if your blend door moves when you turn the knob from cold to hot and vice versa. When you are done make sure to cover the whole up.
5) If you dont feel the blend door moving then it is bad.
Hope this helps.
2006 4.7 4x4 QTII, Class IV TOW
MODS:HD OME Coils and Shocks, Wrangler Silent Armor 255/70r17, Magnaflow