I second the Power Max converter. Your converter is probably located under the ref. Remove the screws that hold the grate on and it should be screwed to the floor. You will need a Allen wrench set, a cheap Volt Ohm Resistance meter for checking the converter output. Disconnect both house battery cables, remove the attaching screws, unplug from 120 AC and carefully put the converter and attached DC wires out from under the ref. With one output lead disconnected, it should be putting out 13 - 13.5 volts DC when plugged into 120 AC. WFCO converters are not the only ones that go bad. When the problem is resolved, hook everything back up and attach the battery cables.
Good luck.