Yup it's wierd. Got a 5th wheel and turns out the hazard lights are engaging the trailer brakes. All other light and brake functions are normal. The truck was wired years ago by the original owner. I assume professional install because it also has a receiver hitch and under bed gooseneck and 5th wheel support installed. I don't know if it's always been like this or a problem that has cropped up. Any recommendations on where to check?