I recently picked up an 07 sporty as a project bike. I've got the back fender off and discovered a small black 'box' patched into the harness that runs back to the tail lights/turn signals. It plugs in-line with the harness under the seat. About 4 inches of the wiring on each side, terminating in a plug. My wiring diagram shows a brake light adapter for the 1200N model, but this is a C.

What the heck is this?

 

Brake light adapter was added as a option. So turn signals go bright with the brake light when you hit the brakes should also have red lens on the rear turn signals instead of yellow ones.

 

Yup, red turn signal lens in the back. That's probably it, thanks! I'm going to cannibalize the connector to make a harness for the new light config I'm putting on.