Which one is house and which one is chassis?
If the power shuts off with the " salesman's switch" I would say house batteries.
Tim
Engine off, BOOST switch off, stick the voltmeter in one of the sockets.
Check the volt reading, then turn on headlights and switch to high beams.
If the volt reading stays steady (does not drop) then that socket is powered from house batteries.
If the volt reading drops, then that socket is powered from chassis batteries.
In my 2003 U320, left is chassis and right is house.