12 volt Radio shuts down when disconnect Shore power

I have been troubleshooting a no spark condition with the help of two Mechanics and all the help online here...
We have changed all the Ignition Devices So now I believe its an Electrical problem. Some Crazy thing area happening... which I am not sure if they were there before I change my Engine Harness...
My 12-volt Radio shuts down when disconnecting my 120v 30 Amp Shore power. But it just buzzes. I have some other Electrical problem such as some devices aren't working either. Like my C-Charger 20 Amp original unit. Windless.

Any idea where to start?
thanks.
1998 DA 5.7

Nothing to do with your engine not running, it's a 12 volt system. If it cranks, like you say, it should run.
So no joy with the new harness ? Your running out of things it could be

Verify that you have good strong batteries. I suspect a bad one(or two) that are robbing all the power and causing the gremlins with the 12 volt systems. ecm needs a solid power source as well as the windless and everything else for that matter.

Just checking voltage.. with the battery selection switch to off.. everything have 2 to 4 volts. Pulsing...switch on A or B or both the same.. took all the smaller wires of the positive.. same things.. faulty Switch?
Full 12. 8 volts with any position.. btw. Batteries only a year old
That's with no shore power.. unplugged