[99gmcFchatt]

I have a 99 Yukon that will not switch the air (or even heat) to the dashboard vents. It switches fine from floor to defrost positions, but when I turn it to the dashboard position, no air comes out and I can hear loud "air flowing" noise (especially when the air is on max) coming from all parts of the dash. It's almost like air is flowing all throughout the dash, but not through the vents on the dashboard. Any ideas?

 

[30 Yr GM Tech Burn-out]

sounds like youve got linkage problems with your mode doors. Look straight up from your gas pedal, On the side of your hvac case. See if you can tell if your linkage is broken.,or, just fell apart. You can identify it by rotating the mode knob while watching under your dash.(key has to be on) There should be a spring between a couple of plastic pieces, that slide on the linkage. GM sells just the linkage kit if ya need it.