The mystery deepens. Airstream sent me a wiring schematic. In the entirety of the 12v
wiring system there is exactly one 8 gauge white ground wire. It is connected to the ground bus bar (which is grounded to chasis). On the wiring schematic that wire leads to a caption that says to look at other pages, but the rest of the 12V
pages are wire route schematics, not wiring diagrams.
Based on my knowledge of what's under the bed (electrical, but could be monsters) I know the ground bus bar is grounded to chasis and there is a larger white wire going in (last I looked I didn't pay attention to size).
So, one white 8 gauge wire, going from the ground bus bar to the splice in the picture in OP, spliced to probably a 10 gauge wire that goes into the frame (cant say if it is grounded to frame).
If it is grounded here, that seems not only redundant but bad. If it isn't, I can't figure out what component would have a ground wire coming up through the shell at this point.
Any thoughts? Does anyone with a newer model (mine is 2011) have a similar wire by the water heater?