Odd Battery Wiring Configuration in old Motorhome

That year pace arrow , under the hood would be a diode isolator, and a emg start relay, to jumper the batteries together ( I don't think the bcc became common until a few years later, PA was not the top of the Fleetwood lines)

My guess is the diode isolator died, and they tied everything together house and chassis

A few pictures would help, put them on some place like tiny pic or photo bucket, and put the links in a post