Troubleshooting Trailer Light Turn Signal Functions Reversed on Trailer
Updated 04/18/2011 | Published 04/16/2011
Question:
We have a 2009 F150 and just rewired the utility trailer. Now, when we put the truck left turn signal on, the right turn signal flashes on the trailer, and when we put the right turn signal on the truck, the left turn signal on the trailer flashes. We switched the yellow and green wires and still have the same problem.
asked by: Linda
Expert Reply:
If you used a wishbone type of wiring on the trailer, it could be lending to the issue you are having. With a wishbone wiring harness on the trailer, the running light signal is split at the plug and carried down two separate wires; one for the left (yellow with brown) and one to the right (green with brown). If it was these wires that got switch and not the turn and brake wires, you will still have the blinker problem.
What you will need to do is use a circuit tester like # PTW2993 and test the functions of the wires. I would start by testing the connector on the truck without the trailer connected. If the signals are all correct, then you know the problem is on the trailer side. If the signals are not correct, then something is wrong with either the wiring in the truck or the converter box on the harness and it will need to be replaced.
Next, connect the trailer and test the functions of the wires coming from the plug. Yellow will be left turn and brake. Green with be right turn and brake. Brown will be running lights. You will just need to make sure the function with left turn and brake goes to the corresponding wire on the left tail light and do the same for the right tail light.
The brown wire or wires if it is a wishbone harness will need to go to the corresponding running light wire on each tail light. If it is not a wishbone harness, then the brown wire will go to one of the tail lights and a jumper wire will go from the brown wire to the other tail light.
Michael H.
4/18/2011
If you used a wishbone type of wiring on the trailer, it could be lending to the issue you are having. With a wishbone wiring harness on the trailer, the running light signal is split at the plug and carried down two separate wires; one for the left (yellow with brown) and one to the right (green with brown). If it was these wires that got switch and not the turn and brake wires, you will still have the blinker problem. What you will need to do is use a circuit tester like the Quickee # 3808, and test the functions of the wires. I would start by testing the connector on the truck without the trailer connected. If the signals are all correct then you know the problem is on the trailer side. If the signals are not correct then something is wrong with either the wiring in the truck or the converter box on the harness and it will need to be replaced. Next, connect the trailer and test the functions of the wires coming from the plug. Yellow will be left turn and brake. Green with be right turn and brake. Brown will be running lights. You will just need to make sure the function with left turn and brake goes to the corresponding wire on the left tail light and do the same for the right tail light. The brown wire or wires if it is a wishbone harness will need to go to the corresponding running light wire on each tail light. If it is not a wishbone harness, then the brown wire will go to one of the tail lights and a jumper wire will go from the brown wire to the other tail light.