Troubleshooting a Left Trailer Turn Signal That Blinks when Right Blinker is Applied

Updated 07/28/2020 | Published 05/30/2014

Question:

I have a 8 / 4 trailer and I get a right signal and brake, but when I pit it to left turn I get another right signal. Here is what I did. Brown wires to both lights yellow to left and green to the right and grounded white to trailer frame. What did I do wrong

asked by: Randy

Helpful Expert Reply:

Sounds like you wired both your left and right turn signals to your right turn signal. To correct this you will need to rewire your trailer. Since trailer wire colors can vary (not usually) you will make sure you wire by function and not just color.

The brown wire from the 4-way on your trailer is the running lights circuit and will need to be run to the running light circuit of both assemblies. This will be the lower illumination circuit. Typically the wire color would also be brown.

The green wire of your 4-way is the right turn/stop signal and will need to run to the right taillight assembly's stop and turn circuit. The yellow wire is the left stop and turn circuit, it will need to be run to the left taillight assembly stop/turn circuit. The white wire of the 4-way will need to be ground to the trailer frame.

I attached an FAQ on trailer wiring that you should find informative as well.

expert reply by: Jameson C

Jim S.

7/19/2020

No brake lights on trailer and left turn works signal works fine but when right turn is Activates. left turn on trailer comes on.Got the wrong one the first time , and this one isn't working from you guys I'm at $130 so far and frustrated.

Chris R.

7/23/2020

Can you tell me what model vehicle you have along with the particular model harness you installed? There are definitely some circuits getting crossed here, but it's possible the issue is on the trailer side. Have you tried testing the actual connector on the tow vehicle for power? I would test each pin with a circuit tester while running through the light functions to see if you get appropriate power.

Jim S.

7/23/2020

@ChrisR Guess I put too much grease on ends and dis not make contact. After a few times of re connecting , It is working correctly. Lesson, not so much grease in connector.