Heater/defrost problems

[nikwho]

Hello all, its getting close to winter and I want to get this fixed. My '83 has a/c. When the switch is in the a/c position, it blows hard. When the switch is in the heater or defroster position, It blows but only very softly. During recent rain storms I have had to use a towell to wipe off all of the windows. Kind of dangerous. The blower motor slows down noticably so I dont think that its a duct thats disconnected or anything. The a/c is not hooked up. It will not blow hot air when in the a/c position. Any thoughts??? Thanks guys,
Nik