My94E320

My 94 E320 has a a/c problem, whenever I turn on the a/c the middle vents blow cold air but not cold enough but the outside vents blow out hot air. I've drained out all the freon and put some new fresh freon and it still won't work. Now that winter is here i try turning on the heater and instead of blowing out hot air it blows out cold. The fan works and so does the blower, does anyone know what the problem is and if so where could I find it so I can locate it and fix it. Please help and thanks!