I had a disconnect on the battery neg to frame wire and thought that would be ok. Nope!
Turned out that because the frame is the neg path for both 120v and 12v, that I still had a neg path aside from the battery to frame wire, when the shore power was plugged into the inverter and something weird was happening the way the inverter was wired so the "ground" wire in the 120v wire got to the "chassis" of the inverter which got to the RV frame.
Anyway, it was complicated. Can't remember all the gory details of which path went where or why I had it like that.
Bottom line is when the battery disconnect on the neg wire was "open" and the shore power cable was in the inverter, I still had 12v lights and fans working in the RV
So as others a trying to warn about, you can have another neg path somewhere, but if you have the disconnect on the battery pos wire close to the battery, you won't have another pos path somewhere.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.