AC vents do not fully switch over, IE: no max A/c

[kd7yar]

Sorry if this has been answered but I could not find a question referencing this problem. I have a 2005 xlt and when switching the vents with the AC on it will move from front, to floor, to defrost, but there will still be some blowing from the floor no matter where the setting is at.
When I put it on max AC there is no increase in the amount of air that blows out as if the flaps are not moving all the way or are stuck. It used to increase almost two fold. Now that it is getting 115 out here, I need to fix this issue.

 

[cmyva]

Having the same problem. I'd like a fix also

 

[TheJackal]

It could be a vacuum issue, or one of the doors are stuck.

You might need to do a little diagnosis on this issue to find out exactly which it is.

Most likely a stuck door or vacuum valve, as a vacuum leak causes it to default to the defrost vents