Troubleshooting Trailer Wiring of Truck that Stopped Working After Year of Not Towing

Question:

Have a truck that hasn’t had a trailer on it in about a year. Last when trailering lights worked fine. I hooked trailer up with no lights turned on on the vehicle, the right rear trailer light was on. Turned on lights for truck and no lights on trailer. Turned blinker on and truck parking lights started blinking . With trailer disconnected truck lights are fine. Trailers work fine on other trucks 4 to be exact. Thought?

asked by: Scott T

Expert Reply:

Sounds like the trailer wiring on your truck has some shorts between circuits and needs to be inspected. It's possible during the year the truck didn't tow something damaged the wiring. Typically it's corrosion that develops on the pins of the connectors or the wiring which will cause circuits to quit working so I'd check for that first and clean as needed.

Looking at the picture you submitted it looks like there might be some wiring issues as well. Looks like some circuit may have been unplugged from the connector so you might check to make sure all of the circuits are ran to the correct pins of the 7-way like in the diagram I attached.

You can use a circuit tester like part # PTW2993 to test the pins of the 7-way or the wiring to verify the correct function to match to the pins of the connector.

expert reply by: Jameson C