No 12 Volt appliances working with engine off and no 110

[wcs]

We have a 2004 Ford Sportsmobile that we bought used and have taken a few road trips in it. This is no doubt a raw beginner's question, but it seems to me that the 12 volt appliances should work with the van parked , engine off and no 110 plugged in. The house batteries are showing between 13-14 volts on the display, but the 12 volt appliances- interior lights as an example- do not come on unless I start the engine or plug in the 110.

What am I missing ?

Thanks.

[Ford_6L_E350]

You may have a bad fuse from the house battery.

Mike

[daveb]

There also may be a house battery switch or main control 12 panel switch. Many vans were equipped with a way to dissable the 12 volt system via a single switch. It can be a relay similar to the battery separator but in most cases it was a manual operating high amp switch.