DC Power

If you have rig disconnected from 110vac power, the roof AC will not operate. If you have the auxiliary/house battery switch in "on" setting, you will have 12 volt dc power to your, furnace and AC controls, interior lights, appliance controls, fresh water pump, etc. If auxiliary/house battery switch is off, your house batteries are disconnected and you should not have 12 volt power to interior lights, etc. The purpose of the switch is to disconnect your batteries when rig is not being driven/in storage, so that battery will not be discharged by parasitic loads like alarms and appliance controls. Learn how the 12 volt system works including how the converter/charger keeps the auxiliary battery charged when rig is connected to 110vac and how the engine's alternator charges the auxiliary house battery when rig is being driven. Battery terminals must be kept clean and tight and electrolyte levels must be maintained above the plates with distilled water. 12vdc to 110vac inverters are not magic, typically, they can power low wattage 110vac devices like laptops and cell phone chargers and draw current themselves to operate from the auxiliary/house battery. House batteries may last up to ten years if kept charged,not overcharged, and electrolyte levels are maintained and converter charge is working properly. Buy a cheap digital multimeter to monitor battery voltage, set it on 20 volt DC setting to check house battery voltage.Should be 13+volts when rig is connected to 110vac power, 14 volts when engine is running, 12.6 volts when rig is disconnected and auxiliary/house battery switch is set to "off". If battery voltage is 12 volts or less, battery is discharged.