2001 Ford E-Series Van AC blowing through defrost only.

I'm working on a Ford E450. The ac is blowing through the defrost only. I understand that this is the default setting. From my research, it is common for a vacuum line to come lose. I took the dog house off on the inside of the bus and found some of the vacuum lines at the back side of the engine near where the transmission connects. There is a red plastic vacuum line that has only one end connected. The other end is not connected and there isn't a rubber boot on it. I started looking to find where the boot was and I can't find it. I did locate a small black plastic cylinder that appears to have the mushroom type end that a boot would slide on to. I am trying to find some sort of diagram so that I can make sure that it is correct. Any help is much appreciated.