[AZKen]

Sorry, should have said remove wheel. The brake switch is just an on-off switch. Power comes in on one terminal and goes out the other when switch is activated. Doesn't matter which is which. Power then goes to the T/S and eventually to the brake bulbs. Be sure stop switch is operating properly.

A new T/S switch and fixing the grounds sounds like you will have it all solved. The ground is ALWAYS an issue. The bulb base touches the socket, the socket touches the housing, the housing is screwed to body, body bolted to frame, frame cable to battery negative. A long and tortuous path that needs refurbished now and then. The test ground jumper you did proves that. You can do things, like that wire stuck in there, to add to the ground contact. But shining it to clean metal, new hardware and a coating over some of it is best.