I just tried to wire up a 7 pin wire harness to a 2008 F150 which has both plug inputs for a 4 and 7 wire. I wired the left turn signal (yellow) into the 9 oclock screw. wired the right turn signal (green) into the 3 oclock position. I wired the running lights from both (yellow/brown,green brown) into the running light screw which I believe is 11 oclock. I wired the ground into the minus at 7 oclock and nothing works. Can someone point me to a wiring diagram.

The trailer lights I just bought from NAPA. They are both two wire with the mounting bolts being the ground. The right has a green and brown wire which I spliced the green to green and the brown to green/brown wire on the trailer. the left I spliced the yellow to yellow and the brown to the yellow/brown wire on the trailer.

Is the running lights (which I combined from both trailer lights and plugged into the running light screw at 11 oclock my problem. Or is it my ground. Do I plug the trailer ground into minus. Please help.

 

How to Wire your Car or Truck for Trailer Lights

 

Did your truck come stock with the 4 flat wiring harness? If so, did you use a converter type wiring harness that basically converts the 4 flat to a 4 flat and 7 round wiring harness? I'd say more than likey it's the ground. No matter where you wire any wires for the 7 round, you should be getting power to that pole as long as you have a good ground. Seems like you did it correctly based on where you wired things as described.

 

If the lights are two-wire, wouldn't one of them be ground? Or are you saying that its a two intensity light (ie brake and running)?

Is the TRAILER grounded? If you are using the frame as ground, and don't connect the ground wire from the harness to the frame, then you won't get any results at all. However, using the trailer frame as ground, while good practice in general, hardly ever works correctly for lights. Instead, run a ground wire to the frame (for safety) AND to each light. Make the two-wire lights into three-wire lights, and just connect the ground wire to the mounting stud. Never depend on the hitch ball or the frame for ground on a trailer, always run a dedicated ground wire IN ADDITION to the normal frame-frame grounding.

 

The bolts connecting to the frame act as the ground on the trailer. The two wires coming out are for the brake/turn signal and running lights. The truck came with a double plug, 7 and 4 wire so you can use either. The trailer has two seperate wires as well for brakes but I have disconnected them in order to work on the lights. Could I have blown a fuse in the truck? All lights work on the truck.

 

Check your 7-way with a test light to make sure you're truck is working first. Put the alligator clip of a test light on the ground pin and then check all other functions. There are separate fuses in the truck for the trailer connector.

Also, if the bolts of the lights are supposed to act as the ground to the frame, then you must connect the ground pin of your plug to the frame to complete the circuit. The diagram I linked shows it all well.

 

Yes, truck is connected to a wire that is bolted to the hitch of the frame.

 

While it is important to make sure that your trailer is grounded (the frame, that is), it rarely works properly for lights. Add a dedicated ground wire from the wiring harness to each light, and connect it to each light's mounting bolt.