Where can I get a trailer harness for the W250? Any recommendations?

 

Maybe overkill for most, but good if you're concerned about electrical fire safety, adaptability, and failed circuit safe operation. Bonus is heavy charging circuit for the fiver and beyond.

https://www.dieseltruckresource.com/...e-t305370.html

 

There are wiring harnesses that simply plug into your existing wiring harness in the back giving you all your necessary lights. They are fairly common and should be able to find one at any auto parts store or trailer supply store. As for battery and brakes, you can buy heavy gauge 2 conductor wire from the same place. Add some circuit breakers and your good to go. Not that hard to do.

 

This is what I did.

I used this one from Tow ready...or similar supplier... # 118317 . This plugs in to the factory wiring and gives you 4 pin lights.

Then I paired it up with a 7 pin trailer plug and harness, Tow ready # 20215 that accepted the 4 pin, and then had 4 wires to add to. One ground, one Batt power, and one from your brake controller, and a reverse light wire (I did not use that). Worked very well.