Help with brake light switch wiring please

I have a 99 WR400. When I got the bike it didn't have the rear light on the fender. I removed the seat and found what I believe are the tail light wires, one blue and one black. My brake light switch has a green with yellow tracer and a brown wire. The tail light has a black, red and yellow wire. Can some one please help me figure out how to wire the brake switch in? This is probably really simple but I am having a brain fart and cant get my head around it. Any help is welcome.

Your bike didn't come with a brake light from the factory.  You may have to cut the tape off the wiring harness harness and expose the wires.  Yellow is hot and black is ground.   There is a yellow going to the throttle position sensor, don't use that.  You can access a yellow you can use at the light switch connector.  You need to run a wire from yellow to either wire of the brake switch.  Then from the brake switch to the brake light.  


You've probably got a pressure switch on one of the master cylinders and an aftermarket tail light.


Most likely the black is ground.   Hook the black to a 12V battery negative and touch the others to positive.  This should show you which one is brake and tail.  


With the wires you found under the seat, black is ground and blue is for tail.


I wired it like you said. I used the yellow at the light switch sent power to the pressure switch and back to the light. It has a running light and brake light. Works great. Thank you for the help

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