A/C vent selection broken

I have an 03 GT and my A/C works fine save for one problem. It goes to my windshield. Whenever I put any air to the vents it goes to the windshield instead, however I can put air to the floor.

I took my control unit half way out thinking it might be an electronic problem. However before I disconnected it I noticed something. When I put the A/C on or the vents on I can here a continuous air sound. I hear the same sound only briefly when switching between the floor and the windshield. So I’m guessing it’s a presser system..? Can anyone help me with how to fix this problem myself if I can?

thanks i'll check that out, how much do you think the replacement lines will cost me? And more importantly were can i get them?