Re: 2005 JGC Air Flow Knob Issue
Sounds like the frond mode door actuator isn't working properly.
These things can be re-calibrated with a starscan, but I haven't heard of anyone having it done. There are also diagnostics on the climate control system (including the operation of the actuators) that can be performed...but it requires a starscan again!
I think if it was me, I would take a gamble and try replacing the actuator - it's not particularly difficult to get to, and I don't think they are overly expensive. If that doesn't work, you may have to take it in to get properly diagnosed rather than tearing things down to visually see what is not working properly.
You can gain access to the actuator through the drivers side instrument panel silencer. Once that is off, it's just three screws holding it in place.