Troubleshooting No Turn or Brake Signals on a 5th Wheel Trailer

Question:

signal and brake lights not working on 5th wheel. they work on truck but for some reason on 5th wheel the running lights work but nothing with the signal and brake

asked by: ROBERT P

Expert Reply:

Thank you for all of the info!

The best way to determine where to start is by checking the turn and brake signals on your truck connector with a tester like part # PK12741 which plugs right into your 7-Way. The trailer lights are on a different circuit from your truck tail lights (unless you have an older truck with a splice-in wiring kit) so it's quite possible that your truck lights are working fine but the issue still lies with your truck wiring.

If the tester shows that the truck is the problem then look at the fuses related to stop/turn signals, which will be on the same circuit. If the fuses look fine then you need to check the wiring for those circuits, including where they connect into your 7-Way.

If the tester shows that the truck is fine then you'll need to look at your 5th wheel wiring for a fix. Check the grounds for those lights as well as the wiring and any connections to your trailer side 7-Way connector as that's where problems can exist as well.

If you find any wiring that needs to be fixed then you can use 16 Gauge Wire # DW02359-1 (sold by the foot) and Heat Shrink Butt Connectors # DW05744-10 to replace the wiring. You can also add dielectric grease like part # 11755 to your wiring to help protect it from corrosion and the elements to prolong the life of your wiring.

Attached are some videos for you to check out.