Got a nasty surprise today in my garage my 5500 on fire at the rear end, nothing crazy but bad enough to burn up some electrical. Haven't had a real look at it but i'm confused how it happened. Truck hasn't moved since friday, why would something happen today? Considering very few wires have power with everything off. The 7 prong plug I believe is the only thing that would have power there with truck off? There is the 2 trailer plugs, back up camera and taillight wiring there. Other then adding the backup camera I haven't touched any wiring on the truck and no problems at all in nearly 2 years. Obviously I need to tear apart all the wiring at the back of the deck and look at it but i'm wondering if I should potentially be looking further at anything? Shouldn't a fuse have blown first?
There is a +12V line in the trailer harness that keeps the brake battery charged, depending on the age of the truck it can be continuously hot or activated with the ignition. Trailer plugs are notorious for causing electrical problems, it's the first place I look if there are problems with signals or lighting of any type. I take the plugs apart and seal them with polyurethane roof and gutter sealer plus plenty of fluid film every time a trailer is connected.