2000 f 250 air conditioner problem

Hey there I am new to the forum. I have a F250 2000 diseil. The air conditioner stoped blowing out of the vents on the dash and nowwill only blow out of the defrost vents by the window no matter what setting the air is on. I had this happen on my work truck but the dealership fixed it. I dont have the money to take it to the shop and was wondering if anyone had any suggestions on how to fix this or have had this happen to them. the air is still blowing cold but it is like something has come loose or something. any help would be appreciated. thanks kyle

there is an electric vac. pump (I think it's on the right fender well) that goes bad and the positions wont change. good place to start.