7 pin umbilical connected while shore power connected causing short and melted wires.

I have a 2021 Mallard Pathfinder 17qbh. Though I'm not making a habit of this, I had the trailer connected to an outlet in the garage and the 7 pin connected at the same time. Immediately, a charge seemed to back up into the wiring going from the 7 pin to the battery of my truck, melting the 12 gauge wiring and smoking. Has anyone encountered anything like this before on their trailer? Searching on whether one can have both of these plugged in at the same time I see varying responses. Even if you are not supposed to do it, it shouldn't almost set fire to my truck, right? Thanks for any insight!


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It's an aftermarket Hopkins 7 pin that was hooked up to my 4 pin on my Kia Telluride by Camping World. They are diagnosing but seeking some owner feedback.


Well-known member
Only two things will cause a wire to melt like that 1) dead short in circuit 2) excessive load(amp draw) for that wire & both would be on a non-fused wire OR fuse to large for that wire. Somewhere that circuir has a problem, most likely dead short - wires crossed up. Good Luck
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Well-known member
It's normal to have bi-directional flow of power between truck and trailer. With factory equipment only, plugging into shore power would cause the Power Converter to supply power to the battery, which would also be shared by the truck. Absent shore power, the truck batteries/alternator will supply power to the trailer battery and other circuitry.

For those wires to overheat, something at one end or the other was drawing a lot of power from the other end. To run it down, you'll probably need a clamp-on meter that measures DC amperage.

But this almost certainly has something to do with the way the aftermarket gear is hooked up.


Well-known member
Camping World??? Well they won't blame themselves. It take almost a direct short to burn open 12ga wire. This is not rocket science. A short can happen in a connector that has not been properly installed. If a wire comes loose and shorts, it becomes a fusible link. It takes 174 amps to melt open a 12 gauge wire. The commercial insulation will melt at lower currents do to the heat involved.