Lx545

I need the wiring diagram for the harness that goes from the front of truck to the rear plug on the frame rail for the tail lights. I have lost power to the running light portion of the 4 blade connector. All other lights function properly. Haynes manual is no help. Any help is appreciated.

white89gt

https://www.f150forum.com/f6/7-pin-plug-trailer-451269/

Lx545

Thanks. It looks like since this truck didn't come equipped with a tow package it's missing three relays. It looks like it needs the trailer tow battery relay and the parking lamp relay. Kind of silly to have a 4 blade at the back and not have all the voltage to it. I hope it's as simple as it's looking.

akdoggie

4 pin has no power wire in the grouping. It is left turn (yellow), right turn (green), running lights (brown) and ground (white). There is no wire for brakes or rear power in the 4 pin system.

You can buy a Hoppy or other brand of quick connect for adding the plug. It is just plug and play. If you are trying for power to the trailer brakes and battery power, you will need the 7 pin plug. Otherwise for most trailers, the 4 pin is sufficient. You only need to do the relays if you go to the 7 pin system. The 4 pin is nothing but draw from the main line for each wire.

white89gt

^^^ Correct. Only a 7 pin has what you are expecting.

kd4gij

Check fuse 5 under the hood.

Lx545

I swapped a couple relays in the tow battery position and the running light position and it brought the power through to the correct wire on the 4 pin plug.

Lx545

The trailer tow battery relay feeds fuse 5 on the diagram which fuses the running light relay which is what feeds the running lights even on the 4 pin plug is my theory anyway