Defroster

My truck wont blow any air up to defrost the windshield. Its a 91 1500. The air will go to the middle vents and feet but not the defroster. What do i have to do to fix it?

Danzig, there is a hose or fiber tube that runs from your heater unit to the vents in your dash for the defroster. Chances are, it has become disconnected or is broken from just wear and tear.........They don't cost much....but putting one in can be a bear.