The heat sucks when i turn it on defrost or floor, its barely warm at all. It comes out nice and warm when i put it on vent. Whats the deal? 89 f150.

 

hmm, is the mix door actuating fully? maybe if not, one set of vents is getting a higher concentration of hot than the others?

or maybe the defrost just blows across the cold windshield and feels colder and the floor mixes with the cold air before it hits open skin.