What would cause my air not to blow through the vents on fresh air mode, when i press the button for recirculatig the cabin air its works fine. I can hear the air blowing up in the dash when fresh air mode is activated.hope i clarified it a little bit. the car is a 1992 325i. this problem has me totally stumped! any ideas or theories would be greatly appreciated!

That would sound like a problem with the duct doors.

Thanks, what area should i tear into to find it.