Most units don't come with owners manuals, they come with individual appliance manuals instead.
Owning a camper is a learning experience it seems, and as you dig into nooks and crannies you will discover wiring and piping and hopefully you can follow some of it. I have had pretty good success with what I can't see when in a tight space with putting my camera on close up, reaching into somewhere, and snapping pictures.
It helps if you find any devices mounted on walls to take pictures of them up close, then look up any numbers on the devices on the internet. Often you can find them and will learn about their function, operation, and repair through that method.
And then, there is the universal system of knowledge on here, just tell us what the pictures show you and someone will be back to you in a hurry with new information.
Enjoy! Mike