The fuses and relays installed in the 2008 Ford F-350 Super Duty truck allow the vehicle's electrical components to function properly. The F-350 has two fuse boxes, one in the engine compartment and the other in the passenger compartment. Only the fuse box under the hood, known as the power distribution box, contains relays. The relays are much larger than the fuses and are easy to identify.
Turn the F-350's engine off if it is running and open the hood.
Remove the negative battery cable from the battery using a socket wrench. The fuse and relays in the power distribution box are high voltage and could cause a serious electrical shock if you do not disconnect the battery.
Remove the cover from the power distribution box to expose the fuses and relays. The relays are all larger than the fuses. The relays are contained in the slots numbered 1 to 3, 16 to 22 and 53 to 59. To determine which relay is which, refer to page 303 of the F-350's user guide.
