I agree with you completely and suspect the OP does too. I did not interpret earlier posts as suggesting identifying the problem would not be a first step. I thought we were suggesting steps to avoid a recurrence after a diagnosis. So fix the problem and make sure that even if recurrence seems like it will be impossible, we want to correct anything that set the stage for so much damage i.e. wiring and fuses need to be sized correctly. It sounds like he has a real mess and may have to do some rebuilding before he can figure out if wires were bared and shorted, etc.
Since his rig operated without a problem for four years, I think it is reasonable to assume something changed, so the first step may be determining what changed and finding a way to stop that from happening in the future.
I may be wrong, but I think we are all on the same page here. 🙂
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC