How to Attach a Trailer with a 3-Way Connector to a Vehicle with a 7-Way Connector

Question:

Hi, I have a 1987 lance that had an old 3 way plug for running lights and 12v battery connection. I have a 7 way plug in the bed of my truck. I am trying to figure out how to connect the 3 original wires into a new 7 way male plug. After many different configurations, the only results I get are no running lights, or running lights stay on, even when my truck is off. As far as I know the 3 wires should be a ground, running lights, and the 12v charging. If anyone knows how I can get this to work, that would be great. Thanks

asked by: Simon

Expert Reply:

A 3-way trailer connector is extremely rare and they really do not make any sort of adapter that will allow you to use this trailer connector with a 7-way connector. The only option that I have for you would be to replace the 3-way trailer connector with a 4-way trailer wiring harness and then use a 4 to 7-way trailer connector adapter.

It is required by law in most states that your trailer has turn, brake, and running lights therefore if your current trailer's lights do not have these features then they will need to be replaced by a light that does have these features. If your existing trailer lights do not have these features then you can use the Standard Trailer Light Kit with 25' Wire Harness part # TL29BK which comes with 2 taillight assemblies, 2 amber marker lights, 1 licence plate brackets, and 1 24' 4-way trailer wiring harness. If your taillights already have turn, brake, and running lights then all you will need to do is install the Wesbar 4-Way Flat Trailer Wiring Harness part # 002220 on your trailer.

Once the 4-way trailer wiring harness is installed on your trailer, you can then use the Pollak 7 Pole to 4 Way Connector Adapter part # PK12716 to attach the 4-way trailer connector on your trailer to the 7-way trailer connector on your vehicle.

I have attached an installation video of both the wiring harness and tail light kit for you as well.

expert reply by: Conner L