electrical problem T600 - 2003

Strange problem with my truck. I go out to it a few minutes ago to grab a few things and it's dark out. I need a dome light so I flip the switch and nothing. Not a single map or dome light in the cab or sleeper will come on... I figure I left something on over the weekend and the batteries went dead so I try to start it. Fires right up. Voltage looks normal. Headlights, marker lights, turns all of those work like normal. But no map lights and also no 12 volt cig plugs working. Let the truck run for a while all of a sudden I hear what sounds like low voltage beeper beeping. It comes and goes. Sometimes it would change tone. I'll check the fuses in the morning. Hoping it's something simple. Anyone have this problem before? If it's not fuses what to check and look at?

 

Where is low voltage indicator located?

 

I can't find it if it is. It's not co-operating and beeping today anyways. Still no dome lights or acc power. Saw a thread where somebody with a Columbia had a similar problem http://www.thetruckersreport.com/tr...167579-2003-columbia-no-power-outlets-no.html Everything in the fuse box is ok. Has to be a wire somewhere #### I hate electrical!!

 

Low voltage regulator. Bypassed it.