distrabution selection
 

i have a 99 chevy silverado 1500 2wd 5.7L automatic. the problem im have is the air from my a/c is only coming out of my vents and i cant get it to move any where else. no defrost, no floorboard air, only face vents. it makes no noise when i turn the knob to change it. it does nothing, but everything else works fresh air, etc. can anyone help?