i have 2002 buicl lesabre limeted the a/c fan blower changed to windshield level and it wont change to floor or mid why?

I have a similar problem with my 2002 LeSabre Limited – see my post about other problems. When I got it, the A/C would only blow out the windshield vents no matter what buttons I pushed. Recently, after fooling around with the cigarette lighter plug under the dash, I found the next time I started car it blew out the mid-level vents, which is better, but still will not change to any other settings. At least these vents are better than the way it was, but it would be great if it would change when the buttons are pushed. BTW, the display does show the vent output is changing from floor/mid-level/windshield when the button is pushed, but the actual output doesn’t change. If anyone can tell us what controls the air direction, it would help both of us. I don’t think the vents are vacuum actuated like on my other cars, so I'm assuming a vacuum leak is probably not the problem. Thanks for any help, Charlie

i had a bad battery. changed to new bat. then had the car connected to a computer went to hvac there were codes for this problem. relearned computer function for this and solved problem.