Ok I bought a 12 volt in dash stereo which I installed in the motorhome end of my 1978 Dodge Sportsman.

What I did
Removed a wall mounted 12 volt light fixture.
Using the pos & neg wires from the removed light fixture I hooked up to the stereo.
Problem
Upon connecting the wires properly the rest of the motorhome lights dim way low. Also a small spark upon connection.

I hooked the stereo into the dash of the cab and it worked fine. No spark...no draw.

So something about running the stereo through the motorhomes converter system is the cause.
Any ideas?
Thanks

edit:
Solved that. Black is live White is ground out of the converter.
I had it backwards.

 

Run a Better Battery + wire and a Ground - wire.... Most of those light grounds are not all that great.... String some new wire for the radio...
Just my 2 cents. Keep us posted on what you fine !!!!