I have replaced the battery, alternator, and starter, the truck will crank but the battery won't stay charged. One mechanic said it was a fuse under the hood. We have checked all the fuses in the power distribution box and none of them are bad. So where do we go from here?
Did you check for valtage anywhere? Did you check for voltage at the applicable fuses? Use a voltage tester. The fuse circuits in the diagram go hot with the key on. The fusible links are hot all the time, should be voltage on both sides of link.
If the battery is down take it off and get it charged, otherwise, we can do any testing.