I'd like to assume that something maybe wrong with your linkages (the things that move when you turn those knobs). On some brands its linkages, on others its a combination of linkages and cables. IMHO, these are your main culprits, as these are the ones responsible for switching cold to hot air or vice versa, or a mixture of both, along with the shutting flaps. Bring your car to a competent AC specialist, I think they can figure it out.