Tank Level Gauges

And the mystery continues:
As I have been tracking the cause of the malfunction, a new issue has surfaced. The generator remote starts switch at the dash functions the same as the levels lights. I cannot start the generator without the motor running. I have checked grounds, loads, etc. but have not found a source. Again, all switches at the dash function except the generator start and all switches at the control panel except the levels unless the motor is running. Everything else functions from 12 volt house batteries normally. The generator control is at the dash, the levels panel is near the rear of the coach. No signs of critter infestation or chewed wires.

The rest of the 12v system works fine as does the other controls on the same panel (water heater, pump, slide outs, room lighting, etc.) it is just the aforementioned gauges. The levels gauges fail while everything else functions, except when engine is running. I find it even more strange that the ignition switch on auxiliary fails to light the gauges but ignition on and engine running lights up the panel. I have opened the panel, check all wiring for a possible short and found none. Fuses checked and all are good. Battery kill switch in powered position. I continue to search! Thanks for the suggestions.

Do you have 12V power otherwise when the engine isn't running? It sounds to me as though the house 12V system isn't working from the house battery or the converter. That may be as simple as the battery disconnect switch being switched off, or a broken battery cable (possibly a ground cable), or a fuse somewhere.

If it's only the monitor panel that's not working, then there's apparently something wrong with the power supply for the panel itself. Usually, though, they're just fed from one of the usual house 12V circuits. It should be fairly straightforward to diagnose, assuming you have a usual sort of setup.