The sensor is a small proximity switch that's located inside the Front brake controller assembly, if you take the assembly apart you can't miss it. The sensor is secured with a small alan screw (maybe 1/16" located on the bottom) and the wire is looped inside the controller housing and soldered onto the controller board. I had to repair mine before; One of the leads broke away from the solder so i just re-soldered it. Drove down the road and it worked fine for about a day. The next ride it quit working on me so i took the controller apart again and found the wire broken again. I think it was probably from the excessive stress on the wire when I reinstalled, that and the vibration. I re-soldered it again but this time i hot glued the a loop on the cable to the controller board to relieve the stress form the actual solder and re-assembled it. works find now. I should have some pics, but they're on my home PC, I'll try to get them up later.