The 7 (seven) prong trailer plug on the bumper of my 1998.5 3500 has 8 (eight) wires going into it. It was hard wired in, along with a 2nd plug in the front of the bed for goose neck trailer connection. Both are wired in at the same spot on the harness.

Does anyone know why this setup has 8 wires in / 7 out? Photo below. The plugs are 7 prong flat. The plug mounting flanges are broken, a prong is gone, and one wire pierced / corroded, so I am going to replace wiring along with plug. There is not enough length to splice and repair just the one wire.

Previous owner claims to have pulled a goose neck trailer. There is no trailer brake controller in the cab, and no evidence of any controller wiring. Without a brake controller, brakes do not work on trailer, right?

Is there a way to tell if truck has factory trailer wiring package? The electrical box under the hood on drivers side contains a Trailer Relay.

Any other tips / suggestions I should know about the trailer wiring?

 

not sure why you have 8 wires... but here is a great pdf that shows the proper wiring of several different types of connectors (4,5,7 pin). which might help you...

I know my ford has a connector under the dash that is for a brake controller... you just have to buy the pigtail to go from the controller to your connector... If you go to a dealer they can usually tell you if your model has one or not by looking up your vin...

 

Thanks for the PDF! I have printed diagrams in the garage, but paper gets trashed.

Looking at my truck, there is a connector under the dash, below the ashtray, and two holes drilled below ashtray. Maybe a controller was mounted / removed.

Will check with a dealer to see what I can learn. THANKX!