I agree that its confusing. However the diagram is 100% consistent with how my 1978 Trillium
4500 is wired.
- white wire is common = negative battery
post (note that it is connected to all sidemarker lights
and tail lights), and black wire = positive battery post. Even more confusing is that in cars, black wire = negative battery post and red wire = positive battery post.
- "ground" is a confusing and misleading term. In cars, the negative battery post is wired to the vehicle chassis (ground of sorts, but not safety ground), and the vehicle chassis provides the negative conductor instead of using wire. In FGRVs, this is NOT done, i.e., the frame is not used except sometimes for brakes