1998 jimmy V6 Vortec..climate control functions is stuck on middle vent

My climmate control functions is stuck on middle vent ,it won't change to defrost or go to the feet.The blower and the heat still works ,it just won't change .thank you for any help.....

My 98 Jimmy does the same thing. Did you ever find a solution?

Do you have good vacuum behind the switch? Is their vacuum to the "ball" under the hood? (on the left side).

the vacume unit that controls that is behind your glove box. If u open it there is a release spring tab on the left top that allows the glove box to swing all the way down.i was having problems with my air blend motor which is right behind the vac unit that could be giving you fits.The long bent flat metal piece that comes out the back of the unit should move back or forward depending on what you want defog heat ect.if you look at my thread i have a picture of the stuff behind the glove box.
http://www.automotiveforums.com/vbulletin/showthread.php?t=967918 hope it helps.

The diverter door vacuum actuator is located behind the dash near the center stack. If you hear alot of hissing when you try to select the mode (vent/floor/defog), then the diaphragm has developed a hole in it. If you remove all the screws along the top of the dash (under the speaker grilles and defroster trim), lower the steering column, and remove the lower trim pieces the whole dash can be rotated back to access it.

The part cost about $15 a few years ago from the dealer as I recall and had to modify it slightly to get it to fit onto the door lever in the limited space. All in all not too bad a repair...a good long handled mirror is a big help seeing behind there. Good luck!