This is from another forum but a great write up none the less How to fix where your air goes. (HVAC) - Dodge Cummins Diesel Forum
I didn't want to start another blend door thread, so I thought I would just post my question here. I have air out of all vent positions on my '07 but no control over the temperature. It is stuck on cold. Does this sound like a blend door problem or control problem?
If I'm not mistaken, the door you want is located above the blower motor. If the 07 is like my 03, you remove three screws on the blower motor (look upward from passenger footwell), drop the blower and use a flash light to look up at the door - it's about a foot up deep behind the glove box. You should be able to see it move (or try to). If it's broken then you will likely find a little piece of plastic inside the squirrel cage fan of the blower when you drop it. DONT try to move the door by hand, it will easily snap!
If I'm not mistaken, the door you want is located above the blower motor. If the 07 is like my 03, you remove three screws on the blower motor (look upward from passenger footwell), drop the blower and use a flash light to look up at the door - it's about a foot up deep behind the glove box. You should be able to see it move (or try to). If it's broken then you will likely find a little piece of plastic inside the squirrel cage fan of the blower when you drop it. DONT try to move the door by hand, it will easily snap!