No running lights, interior or dash lights.

What would be a common problem that would cause the running lights, interior cab lights, brake lights and dash lights to go out all at once on a 78 W-150?
The headlamps, turn signals, work.
I checked the fuses, and changed the headlight switch.
The wiring harness is not hacked, has not even been cut for a radio.
I did add a brake controller, and trailer connecter years ago.
This truck has never had had electrical problems.
Everything worked fine, but my wife used the truck one evening to take the grand kids to the drive in, when she went to leave there was no running lights.

I just cannot for the life of me think what is related to take the lights out, but not blow a fuse, unless the electric brake controller some how went bad, because the light will not even come on in it. It a Kurt controller, so a decent brand name.