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.

 

[Topzide]

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

Not always. My 2014 Ram 3500 is hot all the time. Most newer trucks have the hot constant for lights in a trailer and keeping break-away battery charged when hooked to truck.

 

[cwbyeng1300]

Trailer battery may be backfeeding through the charger to a shorted wire. If the truck was feeding a short it would blow the fuse. Has to be the trailer battery or something that is un-fused to burn up the wires. There is probably a diode in the charging circuit that is bad.

 

[jaxs]

Some people double wrap their dump trailer wires with duct tape to prevent smoke getting out whether key is on or key is off. Roll of duct tape is a lot cheaper than hiring mechanics to put smoke back in wires.

 

[oliver1555]

Replacement smoke is getting harder to come by…

 

[cwbyeng1300]

You can order it online.

Lucas Replacement Smoke Kit

 

[nyone]

Some people double wrap their dump trailer wires with duct tape to prevent smoke getting out whether key is on or key is off. Roll of duct tape is a lot cheaper than hiring mechanics to put smoke back in wires.

We got the "smoke out" of the electrical system joke the first time.

OP have you measured the amp draw? I may look into what fuse supply's that circuit also. You would want the fuse to blow before the wire burnt up.

 

[RancherGuy]

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

Good thing to do. I'm left wondering if the "grounding" of that trailer wire might occur at the truck connection, meaning maybe the trailer itself is fine. I've had to replace my truck's 7 blade connector and noted that the backside of the connector could be exposed to unknown events.

An amp test at the trailer battery and at the truck fuse should produce some good diagnostic information.

 

[jaxs]

We got the "smoke out" of the electrical system joke the first time.

OP have you measured the amp draw? I may look into what fuse supply's that circuit also. You would want the fuse to blow before the wire burnt up.

Maybe so,maybe not but the question remains whether excessive amps,fuse and short circuit were "got" the first time or the second time or the third time or the fourth time or if they need to be trotted out once more.

 

[mrmikey]

Not always. My 2014 Ram 3500 is hot all the time.

Same here, 2019 Ram 1500

 

[JPRambo]

My 2013 Silverado turns off everything after 15 minutes even if key is in accessory position.