[JSeery]

fockfla do you have the wiring diagram? As you can see, it is hot to the dome light switch, ignition switch, the cutout on the generator, the input to the lighting control (which connects to the horn & brake lights), and to the ignition switch. The problem should be in one of these circuits and most likely the cutout. You can disconnect each connection one at a time and see which one stops the arcing (as already suggest by others, the connection to the cutout would be the place to start).