Hoosier Daddy
Earache my eye...
Sounds like you have a short to ground on the positive wire between the brake switch and the lights. That wire takes some funky turns to get to the back of the seat. Check to see if it is pinched or chaffed through the insullation anywhere. Sometimes it helps narrow it down to know if it only happens when you are sitting on the seat or not.
Hope that helps
Hope that helps