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All Trailer Lights Blink When Truck Headlights and Turn Signals are Turned On  


When I turn my lights on and use a blinker all my lights blink including my running lights.When I have my lights off and use my blinkers they work just fine.I just ran all new wiring front to back and new tail lights.The wiring from my truck is a T-one connector I bought from you last week.Boat wiring is 5 wire white,green,green/brown,yellow,yellow/brown.Truck is a 4 wire.Is this the issue..I am lost and frustrated.


Expert Reply:

The wiring harness on the trailer side is what is called a wishbone harness. It splits the running light signal so that you do not have to run a jumper wire from one side to the other. The yellow/brown wire is for the left side running lights and the green/brown is for the right side running lights. That could be what the problem is if you wired it differently.

Make sure that the trailer lights are grounded to a clean and corrosion free location of the trailer frame. Also check to make sure the main trailer ground and the vehicle harness ground are connected to clean and corrosion free bare metal surfaces.

expert reply by:

Gary R.


When the head lights are off my blinks work fine on my trailer but with head light on they dont blink they just light up solid

Etrailer Expert

Chris R.


This type of issue is typically caused by a weak ground somewhere on the trailer. Make sure the main harness ground, along with those for each individual light assembly, are still securely attached to a CLEAN, corrosion-free piece of metal. Let me know if this isn't the issue and we'll keep troubleshooting!

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