I'm not sure about your yr. truck, but all the lightning on my old ford went through the turn signal mechcanism in the steering column under the steering wheel. I gave me all kinds of problems, turn signal wouldn't work - then it would - turn on headlights and the tail lights would go off, hit the brights and the left turn signal would stay on - so check under the steering wheel, the plastic pieces of my turn signal mechcanism had broke which in turn stopped one wire from making contac on the little metal ring. Good luck - that kind of **** can drive ya BONKERS!!!