According to my understanding, the House Battery Switch is there for nothing more than when the unit is being stored without removing the house battery. The OFF position disconnects any internal devices that would otherwise drain the battery. I believe, the truck engine battery is a separate system. And, panel - mounted devices will continue to drain it during storage, unless phyically disconnected.
Interested in knowing more about how the electrical system could be monitored and having learned at an early age about the perils of faulty reasoning when dealing with electricity, I pause those times field tested directions cannot be tracked Ron had a near perfect solution, a few years back, and well before I became interested in the issue.. Having found a proper sized digital device that displayed Volts, Amps,and Clock that he panel mounted alongside the factory gauges, I stopped short of following his lead when it seemed the multi function gauge was no longer being offered.
Reading this contribution and more than a few miles from where the rig is stored, I wonder if the 12V Outlet in the A/V cabinet is sourced by the house battery. So, my question is, can I plug the commonly available cigarette lighter mounted electrical gauges into that receptacle to monitor house battery levels. I am confident the outlet is DC Only. I can only presume it offers isolated power from the house batteries. The similar dash mounted receptacles, which are mounted as a pair, operate from the engine battery.
I apologize for such an elemntary question, but a definitive answer would be appreciated.
