HVAC and or blower motor

[Jance Customs]

My 2000 Dodge Ram is having AC issues. It's blowing cold out of the vents but the dash vents feel like they are blocked off. It seems that the air is being redirected towards the feet because it will blow twice as hard out of the bottom vents. I noticed that I have a black line that is not connected under the dash but I haven't found a spot to plug it in. Any ideas as to what my problem might be? Thanks!