Pictures? Is the switch factory, or someone installed it after? It will be hard to tell unless they did a sloppy job. I assume you eliminated it being a master on/off switch for everything? Is it the water heater? I also assume you know everything in the camper works so there is nothing you are aware of that cannot be turned on/off? You might just have to trace the wires. Could be a cut-off for something that is not obvious like to cut the 12v power coming from the tow vehicle or something....
