We have 8 new F550 40’ service bucket trucks at work. I got asked for help because one would not start out behind the shop last week. There are three mechanics in our shop. I walked up to the big battery charger and the jump cart that has four group 31 batteries and a bewildered mechanic looking at a dead truck. I found several blown fuses and the surprise was the 275 amp non serviceable alternator output fuse. I made a temporary repair with a 250 amp mege fuse and a couple short jumpers. We will have to repace the underhood battery junction box to bring it back to undamaged condition. It looks like they have protected these new computer trucks pretty well to reverse jump starts! I first checked to see what was good and then what did not work. The factory wiring diagrams are great for diagnosis, knowing which fuses are battery hot is key to getting it to run again. The 5 amp ignition fuse was the one that let it run and I had to run through the fuses a second time to catch it open. The new rigs use micro fuses and some are triples, the center is hot and protects two circuits one out each side. Sorry for the ramble but it is nice to get a weekend after a couple weeks of ten hour shifts and no days off. All 8 trucks are upfitted and delivered to their assigned drivers.