Stop and Turn Signal Lights No Longer Work After Rewiring Trailer

Question:

Ive replaced all lights, all connections with heat shrink connectors, walked every inch of the wires down checking for frayed spots, only one found and corrected, new 7 pin plug thats wired to match my receiving plug on my truck 2015 Chevrolet 2500 duramax that also has the 4 pin plug built in combo style plug. All my other trailers work with the 4pin and i cant get the brake lights or turn signals to work on this trailer. Its a 2009 bye-rite 16foot dovetail cast hauler. Ive run grounds from all lights to three frame and also an extra ground from the 7 pin back to the frame, over kill but just process of elimination thing. Please help me. Im thinking my only other option is the one thing i havent done and thats trace all wires on my truck back to the fuse panel. All of those are good as well . Thanks

asked by: Michael

Expert Reply:

The issue you are describing sound like either a short in the wiring or a blown fuse. If you have access to a different tow vehicle or trailer then you can easily determine if the issue is with the vehicle or trailer. If not then the trailer will be easier to test. What you are going to want to do is take a 12 volt battery and touch the positive terminal to each of the pins on the trailer connector. If all of the lights work then you know the issue is on the vehicle.

If the lights still function as before then your only option is to begin tracing the brake/turn signal wire back from the trailer side trailer connector to each light. The brake and turn signal circuit is on the same wire. Generally speaking green is right turn/stop and yellow is left turn/stop but it could be any color.

If the trailer checks out then you will need to begin checking the vehicle. To start you will need to check the fuse box to make sure the trailer stop/turn signal circuits are intact. If they are then you will need to test the trailer connector with a circuit tester. If you are getting power to the pins then there is an issue with the trailer sider trailer connector but if not then you will need to test just behind the connector. If still no power then you will need to trace the wire as far back as possible while checking for breaks.

expert reply by: Conner L