Electrical problem

[rving4us]

I have a problem with the factory 7 pin rv plug in the bed of my 3500. everytime I hook up the fifth wheel and turn on the lights it pops the #79 fuse which are the cab marker lights. if I just back up to the rv and plug it in the light work fine. It is only after the weight of the rv is on the truck. Works the same way using the plug on the bumper. I have gone under the truck and can not find a pinched wire any where. All the lights in the rv work fine. What is left to check? It is a 2014 ram 3500 cummins.
Thanks in advance.

 

[SYKRAMMAN]

Try backing up till the pin is in but don't put weight on the truck, just the pin touching the plate in bed, then plug it in and try the lights, it might be something with the trailers wiring and not the weight.

 

[mtofell]

Look at the J-box on the underside of the 5th near the kingpin. My cord got stuck under my hitch once and I pulled the wires partially out of the box while turning. I discovered it before anything went wrong but the wire junctions were all kinds of mangled and easily could have started acting up.

 

[SYKRAMMAN]

^ that sounds better.