I too am at a loss. The 120VAC System has nothing to do with the 12VDC system. They both share the GREEN WIRE frame ground is about the only thing common.
The 120VAC INPUT to the Converter has three wires coming from the SHORE POWER SIDE being HOT (Black wire) - NEUTRAL (White Wire which must not be connected to the trailer frame ground) and GROUND (Green wire which connects to the trailer ground).
This is a drawing for the WFCO 8900 series Power Distribution Panel which shows this and is kinda hard to follow the grounding scheme.
This is another drawing showing where my 120VAC and 12VDC lines are grounded.
I would use one of these units on your incoming 120VAC Voltages from shore power and make sure all three leads are wired properly. (LOWES)
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Roy Ken
