There are a few online sources that may have the original owners manual for your orphan rig, but, such manuals do not usually go into details of maintenance, troubleshooting and repair, are often generic for more than one model motorhome, and no wiring diagram. There are some good generic how-to books for maintaining any motorhome and include description of the 12 volt DC and 120 volt AC systems that provide power to furnace, water pump, toilet, fridge, and keep your house battery(s) charged plus fresh water and sewage and holding tank systems. As said, there are a lot of "How-to" You Tube videos that will probably serve your needs.
