A/C not blowing properly

I have a '97 1500. My A/C is not blowing with the force that it should. When I have the selector switch in the face position or any of the other two positions, I am getting a lot of blow out of the defrost duct which in turn fogs up the window. I'm assuming that the deflector is not closing off the proper ducts and is not directing the airflow the correct way. Any thoughts or suggestions?