The rear a/c vent blows cold; however the dash a/c vents will either not blow at all, or intermittently but not strong. Once in awhile, a swooshing sound will come from the middle dash vents and it will blow hard and cold and then stop. We have changed the cabin air flow filter, the system does not need freon, and the compressor is working. When we replaced the cabin air flow filter, it was mushy and very dirty; probably had never been replaced. Leaves and dirt feel from the area where filter had been and there was ice. Someone mentioned that the "flaps" were sticking and therefore the cold air was turning to ice. Other words, we have no clue! Thanks for any help you can give.