Quote Originally Posted by Simonlawnservice View Post
I have running lights but no brake lights nor turn signals on my trailer. I have a 4 prong flat on my truck. Where there is a ground prong and 4 female plugs. However the boat trailer has the ground prong and only three male prongs. Does anybody have a solution to this?? I didn't know if I needed to put a 3 prong on my truck or what. All info is greatly appreciated!!!
I think you will find the truck is setup for a trailer with surge brakes, the extra wire is the backup light circuit that goes to the release solenoid for the brakes when backing up. You can buy an adapter to hook-up one to the other. Auto Zone Walmart etc. should have this.