FORD 2010 F-550 v.1 - Manual (Page 310)

Power distribution box
The power distribution box is located in the engine compartment. The
power distribution box contains high-current fuses that protect your
vehicle’s main electrical systems from overloads.
WARNING: Always disconnect the battery before servicing high
current fuses.
WARNING: To reduce risk of electrical shock, always replace
the cover to the Power Distribution Box before reconnecting the
battery or refilling fluid reservoirs.
If the battery has been disconnected and reconnected, refer to the
Battery section of the Maintenance and Specifications chapter.
The high-current fuses are coded as follows:
Fuse/Relay
Location
Fuse Amp
Rating
Protected Circuits
1 Relay Blower motor/Variable blower control
(Dual zone climate control)
2 Relay Electronic shift-on-the-fly (ESOF)
Lo-Hi
3 Relay Heater mirror
4 — Not used
5 30A* Trailer brake controller (TBC)
Roadside Emergencies
310
2010 F-250/350/450/550 (f23)
Owners Guide, 1st Printing
USA (fus)