So no matter what setting it is on, max ac etc.. it only blows through the windshield. Except off, lol. Never really noticed till now, and i do have a guy coming tonight who is interested in the truck so ANY help would be greatly appreciated. Like i said not a huge deal, it works, just cant really think of what would make it do that.

 

Vacuum lines. Check them all. Then check the vacuum ball on the passenger side splash guard. Its a common problem.

 

Couldn't it also have something to do with the blend door? Just a thought...

 

Not likely. The vacuum lines are a common problem.

 

My neighbor had the same problem with his F-150 and it turned out to be the blend door...that's why I chimed in.

 

blend door? info or pics please.

 

Its the door that forces the air where in needs to go. Again the common problem is the lines under the hood for it. You could have a pin hole leak.