Tech Tips (by ALLDATA): Isuzu NPR-HD blows 80-amp fuse
TECH TIPS (courtesy of ALLDATA)
Problem: No electrical power was available in the vehicle. The battery was fully charged.
Details: The technician found that the 80-amp FL-1 fuse was blown. He installed a new fuse, which blew immediately, even with the key in the Off position.
Based on the wiring diagram, the Tech-Assist consultant suggested unplugging the alternator because it was one of the main components connected to the GL-1 fuse circuit. Other circuits had their own smaller fuses, which should have failed if there was a problem in their circuits (see diagram).
Confirmed Repair: The technician unplugged the alternator and the fuse was okay. The alternator was replaced and the vehicle was fixed.