Battery saver ckt. in inst. panel. Check out this you tube. They put the BS ckt. in the panel starting 2002.
(180) Ford SuperDuty Battery Saver Relay Cluster Repair - YouTube
Even though a V10 he covers the vacuum lines in the first part of the video, This is a good video on the vacuum hubs.
(177) Ford F250 4x4 - Vacuum Hubs NOT Engaging - YouTube
This info might help. I did not stay at a Holiday in Express but I have been trying to repair vacuum lines that some 4 wheeling mice ate. You are dealing with a vacuum issue. The vacuum pump is located on the pass. side inner fender. It supplies vacuum to engage the HVAC dampers and Hub...