fan only blows thru the dash vents

[DonDDR]

When I move the knob it does nothing. Just blows thru the vents on the top of the dash. Haven't taken it apart yet, but wanted to know if someone know the most likely fix for this so I can get parts before I tear it all apart. Thanks in advance.

 

[corkey]

it could be the blend door, or it could be a vacuum leak
switch the heat knob around, if it doesn't change listen for the blend door activator,
if no blend door activator noise, than it could be a vacuum leak,