Chevrolet Repair: a/c air flow is poor, dash pot, chevy suburban

Question
I have a 1999 Chevy Suburban with front and rear a/c controls. The rear air flow controls work just fine and air is cold. Problem is the front vents for driver and front seat passenger allow air flow, but does not blow a lot of air. Nevertheless, when we switch the fan from low to high, we can hear the fan speed up and sounds like a lot of air being pushed, but not through the vents. The feet vents in front seem OK. What is causing the limited air flow to the main vents?

Answer
HI STEVE, THE WAY YOU ARE EXPLANING THIS, IT SOUNDS TO ME IS IF THE CENTER PORTION OF THE DUCT WORK IS FALLING OFF BEHIND THE DASH CAUSING WEAK FLOW OF AIR THROUGH THESE VENTS. NOT PUSHING THROUGH THE VENTS AND LEAKING AROUND THEM..HOWEVER THERE IS ALSO A CHANCE THAT THE A/C TO HEAT BLEND DOOR IS NOT OPENING ALL THE WAY TO ALLOW COLD AIR TO PUSH THROUGH THESE VENTS..I WOULD GET UNDER THE DASH AND MAKE SURE THE DUCT WORK GOING TO EACH OF THE DASH A/C VENTS ARE HOOKED UP..THIS WILL TAKE SOME LOOKING INTO AND REMOVING SOME PANELS TO GET AT IT TO LOOK AT..IF THIS IS NOT THE PROBLEM AND YOU ARE HANDY,, THEN THE ONLY THING LEFT IS THE BLEND DOOR NOT OPENING ALL THE WAY. THIS WILL TAKE SOME TIME TO REPAIR BECASUE SECTIONS OF THE LOWER A/C AND HEATER ASSEMBLY UNDER THE DASH WILL NEED TO COME APART AND LOOK AT TO SEE WHAT IS GOING ON..LIKE A STUCK DOOR OR A DASH POT THAT OPENS THIS DOOR IS BROKEN OR JUST STCUK..IF THIS DOES NOT SOUND LIKE SOMETING YOU WOULD LIKE TO DO I WOULD TAKE IT TO YOUR CORNER TRUSTED SHOP AND HAVE THEM LOOK INTO IT..UNDER DASH WORK IS NOT FUN FOR ALOT OF PEOPLE.. I HOPE THIS HELPS YOU,,,TOM..