Ford F-550 Owner's Manual page 70

Driver Controls
When switched on by the operator they provide 10 amps or 30 amps of
electrical battery power for a variety of personal or commercial uses.
If your vehicle is equipped with this
option, there will also be a relay box
with a fuse located inside the glove
box.
The relays and fuse in the glove box are coded as shown in the
accompanying illustration.
70
2007 F-250/350/450/550 (f23)
Owners Guide (post-2002-fmt)
USA (fus)