Replaced vent selector switch, vents still "sticking"

The only functions that work correctly are defrost w/bottom and top and bottom vent. I replaced the selector switch, but that didn't help. It has to do with the blending door inside the dash. How do I get to it? Where is it? I can hear it sticking when moving the knob.

I own a 1996 Ford Thundserbird, and we have the exact same problem. It started 6 months after we boght the car...Weird huh?

There are several posts here and on the Olds Bravada forum on this problem. What year is your Blazer? What I have determined is that on some years earlier than the 200o which I have the switch is easily accessable by dropping the glove box down (there is a spring at the top left which holds it, push that back the whole box turns down - dumping any contents btw) the component is to the left side on top of the heater box. On my 2000 I can see it but cannot reach it because it seems they moved the AC ducting and now it can only be removed by removing the entire dash.

If you are lucky enough to have one that does not have this new ductwork take out the two screws on the unit and unplug it to replace it. Some threads say that you might be able to take the unit apart and fix what is wrong inside - but that seems to be a broken plastic gear so my bet is if you don't replace the unit you will be fixing it again soon anyway.

Question to anyone else out there who is familiar with the configuration of the 2000 Bravada where that duct is in the way. Is there any downside if I cut out the ductwork to make the repair and then glue or duct tape the pieces back in when I am done?

My Jimmy is a 96. I hope it's easy- remember this isn't the air blending door, but the pneumatic vent selector. Has anyone done this before?