Troubleshooting New Wiring on Trailer Causing Right Turn Signal to Activate All Trailer Lights

Question:

Good morning! I rewired my utility trailer cause the 4 prong flat plug got damaged and now the right turn signal flashes all lights including both tail lights on the truck, do you think the problem is at the truck or? Wired as per the old one, white to white, green to green, yellow to yellow and the two browns to the brown from the truck, did I do something wrong?

asked by: Clifford B

Expert Reply:

Since the issue didn't start until you swapped out the 4-Way on your trailer it would seem that the problem is on the trailer end, but normally this doesn't translate over to the vehicle. What could be going on though is that you have a bad ground on the trailer which is causing backfeed on your vehicle side of things. Checking the connectors themselves to make sure they are clean is always the first step. Using some dielectric grease like part # 11755 can help protect and prevent future corrosion and water issues as well.

If you have another tow vehicle or trailer handy you can easily determine if it is the trailer or the tow vehicle itself by testing the trailer to another vehicle or your tow vehicle to another trailer. If you don't have one handy then check the grounds on your trailer. Make sure they are secure and connected to a clean, bare-metal surface.

The next step, if the grounds look good, is to search along the new wiring you installed looking for any places where the wiring may have become bent or where the connection isn't very secure.

If all of this checks out the tow vehicle is the next place you want to inspect. Look at the wiring connected to the prong for the right turn signal and see if that is bent or damaged. If you can't find anything wrong you may need to take your vehicle to a shop and have them inspect it.

Attached is a troubleshooting help article for you to reference as well.

expert reply by: Jon G