Wiring Up a Harbor Freight 4-Way Trailer Connector and Trailer Lights

Question:

I have 4 prong on 2010 Lincoln MKX and 4 on untility trailer, 2 brown and one green and one yellow. My tail lights have a red and yellow on the left and red and green on the right. The book from Harbor Freight says left side connect the yellow wire to the red wire and connect the brown wire to the 2 black wires of left tail light. Right side says connect green to red and brown to two black wires. Well, I dont have any black wires and only have two wires coming from tail lights. Im doing this myself and Im a girl. Please help

asked by: Irene M

Expert Reply:

Lets start with the trailer connector. I can tell you what the functions are so it will be easy to connect to the lights once we determine their functions.

On a 4-Way, you will have one pin that is covered. That is the ground. Right next to it is the running light pin. Then the left turn/brake light pin. And the last pin is right turn and brake lights.

Now, on the lights, since the common wire on both sides is red, I am inclined to believe this is the running light wire. What you will do is attach the running light wire from the 4-Way to one of lights red wires. Then you will need to run a jumper wire from that side over to the red wire on the other side.

On the driver side light with the yellow wire, you will attach the 4-Way yellow wire. Then attach the green wire from the passenger side light to the green wire on the 4-Way.

Now if you have 2 brown wires coming out from one pin (the pin next to covered pin) then that means they both carry the running light signal and you would not need to use a jumper for the running lights. Just run one to red wire on one side and do the same with the other brown wire and light on the other side. Everything else will be as described above. Another tip I can offer is if you look at the backs of the lights where the wires come out their functions may be listed.

I have included a link to our wiring FAQ article for you. There are wire colors listed but ignore them because there is no standard. Instead look at the functions listed.

expert reply by: Michael H