||I have the original owner's manual for my 1988 Mallard Sprinter. I can send you a copy of it for $10.00, to cover my photocopying and shipping charges. It only about 30 pages long and is pretty generic. It doesn't have a complete electrical diagram in it. It refers you to the dealer when you need electrical wiring checked.
For some reason, when I purchased my Sprinter, the wire from the battery to the engine compartment was disconnected, too. I had the local RV shop install one of those battery isolators (available through JC Whitney). Then they reconnected the cable and I haven't had any discharging problems since.