I'm wiring a trailer with a flat four connector, I know the color code, the problem I'm having is: When ever I turn on my running lights the trailer lights go off. Basically the blinker and the brake ligths work fine, but as soon as I turn on the head lights the trailer lights quit working. Any ideas of what's going on?

Mark Ribeiro, September 2006

Is there a tester to tell if a short has been fixed in a trailer without pluging it into the pickup and blowing fuses?

Calvin, November 2010