8 volts with chassis batteries disconnected .
Sorry I missed this the day you posted .
A note from my first owning my coach , I'd get erratic voltage readings at my lighter socket and it wouldn't power anything that was plugged into it .
Turned out a factory installed , chassis battery maintainer solar panel , was back feeding voltage ( at very low amps ) to the dash socket and the fuse was just blown.
I'll look over the pictures you've posted and see if I can spot anything that's possibly wrong.