BMW heating/air conditioning not working?

I have a 95' BMW 318i. My heating/cooling system scarcely works at all. In the summer, the air conditioner didn't work. It makes the sound (as if it's blowing air) but when you put your hand over the openings where the air is supposed to blow from, you feel nothing. This was not too bad in the summer, as I just drove with all my windows open, but in the winter it's freezing! Same sort of problem, sounds likes it's blowing, but don't feel any air coming out. I can't even defrost my windows, they keep fogging up from the inside. If anyone has experienced similar issues or has a good idea of what the problem may be, kindly enlighten me. Thanks.