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How To Install 4-way Connector On Trailer That Has Non-Standard Wire Colors


On my trailer, it looks as though the harness adapter had been replaced but worked fine until the prongs became really brittle this last year. Upon trying to replace it with a new one which has 4 solid wires - Green, Yellow, White and Brown - same as the old one, I noticed that the trailer wires are Solid Yellow w/ adjoining yellow w-brown stripe wire, solid Green w/ adjoining green w-brown stripe wire, and white. I tried connecting the brown stripe wires on the trailer to the brown on the new harness and then naturally green to green, yellow to yellow and white to white. The lights work but the turn signal and brake lights will not work. I have tried different combinations where I was successful in getting the turn signal and brake lights to work but the running lights wont stay on. I have tried 2 different plug adapters on two different vehicles. I am at a loss.


Expert Reply:

I would be happy to help!

Since your trailer has wires that are not the standard colors you will need to identify the functions of each wire before installing the new 4-way flat connector.

The two ways to do this is by tracing each wire back to the light it goes to, or by finding which wire is the ground and then testing the other 3 wires with a 12v battery. You would hook the ground wire to the negative terminal of the battery and then each of the other 3 wires to the positive battery one at a time to see which function lights up.

Once you have identified the functions of your trailer wiring you will install the 4-way connector as follows:

Green wire is the passenger side turn signal/brake light
Yellow wire is the driver side turn signal/brake light
Brown wire is the tail light/running lights
White wire is the ground

I included a link to a helpful article on trailer wiring for you to take a look at.

expert reply by:
Samuel C

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