Burned Up Trailer Wiring

[Jaynen123]

I have a dump trailer that has the hydraulics and battery in a storage box on the front. We plug and unplug this trailer to the truck multiple times a week with no issues. The other day we plugged the trailer into the truck and the wiring started smoking. Turns out the wire thats used to charge the battery burned up from the truck to the trailer battery. Truck side was fine thankfully.

This is the second time this has happened now in a 2 year period and I would like to know whats causing this. Its a pain because i have to replace the whole 7 wire bundle. Only common thing between the 2 times this has happened is I believe it was raining. The junction box on the trailer was dry and i couldn't tell if the plug was wet.

Any ideas what could be happening and how to stop it? I have another exact trailer like this and its never happened.

Thanks

 

[CobyRupert]

It started smoking because it got too hot. It got too hot because too much current was passing through it. Like a LOT of current.

Why was a lot of current passing through it?
1) There’s failed insulation or some type of short to the frame that provides a low resistance path (= large current) for the 12v to “ground” (which is the frame and negative battery post). Given that this happens when it rains, I’d guess a path from a bare spot on an energized wire forms to the frame.
2) The trailer battery is drawing a LOT of current.

Typically, you want a fuse to melt before the wiring does. The fuse should be sized to protect the wiring. Fuses are easier to replace.

 

[claggstractors]

Sounds like too many amps being pulled through that wire. Possibly the battery isolator/charge controller is getting wet and shorting out?

 

[4570Man]

The charge wire is supposed to have a self resetting circuit breaker. I suspect yours is faulty and not tripping. Another possibility is the wire has been rubbed somewhere and it’s shorting out.

 

[Jaynen123]

Thanks guys. There is only a fuse for the circuit on the truck side no fuse on the trailer side. Truck side didnt trip. Definitely no rubbed off insulation exposing bare wire anywhere.

I guess I'll install a self resetable fuse on the trailer side.

 

[alexpops]

You have a short somewhere. Are the lights all operating properly? electric brakes? Trace the full wire runs to/from the junction block and the truck connector and battery (unwrap any sheathing/tape & check the individual wires for chafe). If the wires are all good for the full length, check the connectors (plug to truck) and the junction box -- connectors can get unseated & pushed out the back of the plug then short if close to frame/other connectors. If those are good, check the switch that operates the pump and the pump itself for an internal short. If those check out, check the battery for shorted plates. Any hard bends or areas going over edge metal in the trailer frame are good places to start checking the wire runs.

 

[jaxs]

I have vision issues that limit how far I can see. Bring it and a six pak of Bud Lite to me and I'll troubleshoot it for you.

 

[nyone]

Is this a trailer that's plugged into the truck all the time when parked?

 

[jaxs]

My neighbor had the same thing happen and the mechanic said he had let the smoke out and charged him over $500 to put it back.

 

[RustyA]

12 volt charge wire is generally only hot when ignition is on.