My Majestic was sort of doing same thing. Same as you except, very little going into house battery and taking forever to charge. All wires looked good but upon very close look, many were not in that good of shape after removing one by one to inspect. Cleaned up all except 3 of them that I made new and larger in diameter and made difference with mine.
I couldn't find any diagrams I just went wire by wire. All my fuses are under dash or under hood or in house part, except a breaker switch on generator.
Mine is 2003 which means old style charger that takes longer to charge unlike newer "smart" chargers.
