Troubleshooting Trailer Right Turn and Brake Light

Question:

Signals on both the 4 pole and 7 way are fine, if I hook another vehicle to camper all lights work perfect, ground wire is secured to the frame on vehicle, any suggestions?

asked by: Tony C

Expert Reply:

Since your 4-pole and 7-way vehicle connectors have correct signals and the trailer lights work properly when you hitch another tow vehicle, I suspect that there may be an intermittent problem in the wiring. This could still be on the vehicle side, or it could be on the trailer side. Older wiring can develop cracks and breaks inside the insulation that are not visible and sometimes the action of unplugging and plugging in a connector can make or break that circuit connection. A marginally loose wiring connection could cause the same symptoms, as could corrosion on the trailer plug contact.

You can use a tester like # PTW2993 on the trailer's wire for the problem circuit. When you know power is going in at the trailer connector, apply the tester while a helper jiggles and manipulates the trailer wire for that circuit. If you can cause the light signal to fade/stop by your wiggling it, then you know the issue is in either the wire itself or one it its connection points.

expert reply by: Adam R