Deb and Rick-
I understand your frustration. It took me a couple times before I found the chassis battery cut-off switch, which was not where the owners manual said
it would be.
RVs are not as standard as cars, not as custom as houses. Some manufacturers are better than others at making model-specific owners manuals.
A way to think about the beasts is that the manufacturers (and sometimes the individual installers) get to fold the "standard" equipment and systems into a box of varying size and shape (think boat, but a bit more rectlinear). Your job, as the owner, is to figure out where they put all the stuff.
That said, I find myself reading the coach and component manuals often, and learn something new each time. iRV2 members help you figure out some of the things the manuals don't tell you. In the computer world, the abbreviation "RTM" means "Read the Manual," and there's a reason why it's become an abbreviation, through frequent use.
On the electrical side, you can learn about 12V systems (in general) at "The 12 Volt Side of Life (Parts 1 and 2)," at this link