I have recently bought a 10'tent trlr, with a 12V battery. The battery has a charge and the lights, fans and furnace work when plugged to shore power. But on its own, I have no power. I'm guessing there is a cut-off somewhere, or a short, but I've tracked the wires from batt on in and find nothing. So, stumped. Anybody have any ideas about resolving this? Thanks.