The original converter made by Progressive Dynamics is still in the '74 Class C. According to the owners manual, when plugged into shore power, the converter is supposed to charge both the engine battery and the house battery. Likewise, when the Barth is running, the alternator is supposed to charge both batteries. Question: On top of the converter there are 4 round black knobs, about 3/4" in dia. and it says they are "secondary load fuses". Would they be ac fuses? Or dc fuses? I haven't touched them yet. Today, Tere and I cleaned up the house battery compartment and installed a proper fuse block for the two wires that come from the battery that seem to power all the dc appliances.Thanks for the guidance.

Those fuses will have 12vdc on them when running off batteries and 12vac when plugged into 120v. unscrew fuses 1 at a time to see what they power. This is the problem with changing out interior light with LEDs.