No Right Side Fender or Rear Running Lights on Cargo Box Trailer

Question:

2006 12ft cargo trailer-running lights on tail and side wheels not working. Front running lights still work. Painted front fork that has main ground, ground still works, because when i remove it front runners go out. Could I have messed up ground connection to back lights, all grounds for lights are connected inside the trailer to the frame. Checked truck fuses, everything looks good. Going to circuit test truck connector and fuses to double check. All i can think is its the brown/yellow wires on trailer connector that is faulty. Would painting fork disrupt grounds in back of trailer? Green wire feeds front running lights and then Ts off to back, brown/yellow go directly to wheel well and rear tail lights. All brakes and turn signal lights still work.

asked by: Jay A

Expert Reply:

It's really quite simple to troubleshoot lights on a trailer. The ground as you mentioned is the first thing to rule out, these can be installed differently from trailer to trailer. It's best for all the light to share the same ground which is usually at the front of the trailer on the tongue. This entails tracing wires from the light to the ground, or if you want to rule this out faster just make your own ground close by to bare metal. Then, you'll need to be sure the light has power, check first at the trailer connector to ensure the signal is sent from the vehicle and begin tracing your way back from this to the light in question. This can be done with anything from a volt meter to a simple test light. The running light wire is usually either brown or brown/yellow or brown/green.

I have attached an article for you below which goes over troubleshooting trailer lights as well.

expert reply by: Conner L