1989 Southwind auxilary battery problem

The Aux switch (salesmans switch) is located above the door in a cabinet. One is marked main and one is marked for coach or aux.

Look for Aux batt switch, mine is on the dash. If it is off no interior 12v. Does not affect 110 V outlets, Must be plugged in or running genset to power those unless you have an invertor that is turned on.

My response is in addition to MrWizard. As a rule, the lights are DC and the electrical plugs are AC. More info is needed. Are the house batteries charged? Do you have an inverter? Is the battery cutoff switch on? Present situation of use(park power or not, on the road disconnected, in storage or even parked at home) would be good extra info.

I also have a 1989 Bounder that I have more or less restored. On your electrical issue. Check your inside breaker panel, make sure they are all on. Then if you feel confident, take a circuit breaker to check your fuses in that panel to make sure they are all functioning. You might want to also first check your house batteries condition and the cable connections for cleanliness (ie no corrosion etc.) and that they are tight and snug. If none of that works I suggest you take it to your local trusted RV repair shop. Hope my ideas work for you. Good luck.

How long have you had it?
Are you driving it
Or
Plugged into power
The aux battery better know as the house battery/batteries are charged by the alternator thru an isolator/separator when the engine is running
And from the converter/charger when 120v is available that's generator or shore power cord
Unless you do something that cause charging, you now have a dead battery
Are you plugged into shore power,
Look for tripped circuit breakers then loose battery cables

Do you have a switch for storing the coach, if so it may be on. The switch will separate the coach from the battery so that there will be no drain on the battery