Garry - see if you can find the chassis manual for your coach as running lights are usually powered from the chassis builder. That will be where to start looking.
Then at some point, the coach builder is going to pick up that signal to actually power the lights with. And that is probably where your real fun begins.
However - you might try checking how those lights get grounded too. If it appears they are each grounded individually then move on to the 12 volt side of things.