Oldsmobile/Buick Repair: Buick Skylark Repair, buick skylark, heat control

Question
My heat control on my 1989 Buick Skylark quit working.  I moved it about 1/4 of the way from from cool, and now it leaves the heat on high regardless of where the slide is placed.  All fuses that I can see are good.  The heat/ac selection controls work. The fan operates at all speeds. What can I do to fix this?
Thanks!!!
Ted

Answer
hi ted,well it sounds like maybe you have a vacum mtr stuck.when you move the temp selector lever you are transferring vacum.and opening and closeing a little door.blend air door.look under your dash,there is a large plastic box.prob black in color.you will see levers and vac mtrs.little silver round things with vac hose attached are the lines hooked upare they moveing with the controllers.one is not move it open or shut .and should change from cool air to hot air your prob is right there.good luck.please take a sec of your time to rate my service ty billymac