Trailer Wiring Please Help

[DTro]

Ok, on my Toyota 4 Runner, I have a 7 pin adapter to 4 pin for my Snowmobile Trailer. Also I have a 4 ft extension for some extra slack between the trailer and the truck.

On a recent trip up north. I stopped to get gas and noticed an electrical burning smell.

Upon returning home I checked the wiring and was shocked to find that the insulation on the extension portion (white wire only) was completely melted leaving the bare copper wire. The wire coming directly from trailer was fine.

I didn't get a chance to troubleshoot and just bought some more components and rewired. After I did that, I did not have any trailer lights, but I left it plugged in anyways since I was going fishing and didn't have time to mess with it. Well I drove a few miles and sure enough, the extension white wire melted again.

I'm stumped on even where to start on this one.

[Caleb S]

dtro, did you just extend the wires before taking off to the lake or had the wiring set up been successfully used before this issue?

[Dave S]

Have you replaced any fuses for your lights? Replace the lights also or just wires? Is your ground connection clean where it's connected to the trailer? Check all connections including crimps and make sure they're all good also.

We just had a lengthy discussion about electrical issues in the ATV forum and the topic of melting wires was brought up.

Almost sounds like there might be a short somewhere and the fuse may be too large and not blowing out like it should. This could cause your wiring to overheat and melt the insulation.

[DTro]

The wiring functioned for over a year in the same configuration. It just recently did this to me. I haven't changed anything in regards to bulbs/fuses or wiring.

I agree that a fuse should've blew before it got hot enough to melt.

Oh another note. The 7 pin adapter I have has the three LED lights, and they all function as intented. Leads me to believe there is an issue on the trailer side and not the truck side. It is a tilt Sled Bed trailer and all the wiring is ran through the frame.

Should I just start pulling off lights and try to find something?

[Dave S]

I agree that it is in your trailer. I would check the wires starting at the lights.

But then again, you might want to completely take your lights out and clean the area behind the lights. I mounted new lights and rewired my trailer last year and the ground between the mounting bolts for the lights and the trailer didn't have a good contact (rust). Your sled bed might have some corrosion built up preventing a good ground between the light assembly and the trailer frame.

[DTro]

Thanks for the suggestions, looks like I have my work cut out for me tomorrow

[Dave S]

I hope that helps. Good luck.

[BarryG]

Instead of messing with your old wiring just buy a new set and rewire, it probably would be just as fast and you'd have the problem solved.

[sparcebag]

I've where the trailor tilts,had shorts from the wires rubbing,too short & breaking,and hot grounding out & melting insulation on wires.

I'd start looking there first.

[Papa Grump]

Hey Darren, I had all summer to rewire that trailer for you while it sat in the shed Give me a call and I'll stop over and help out.

[leech~~]

dtro, I had the samething happening, and found out one of the hires running through the trailer tube frame had worn and was shorting out. I used a tester at the front and back of the trailer when hooked up to the truck so power was running through to find the bad one. I cliped the shorted wire at both ends and ran a new wire down the out side since I didn't want to fish the old wires out and try and fish the new ones back down the tube frame! Try that maybe?

[Whoaru99]

I agree that a fuse should've blew before it got hot enough to melt.

Fuse won't blow if the current required to heat the wire and melt the insulation is lower than the fuse rating.

That could happen if the extension wire has thin wire.

However, if it worked before, I'd agree there's a problem in the trailer harness. Sounds like looking around the pivot area would be a good place to start.

[DTro]

Well, I'm back in business!

I started at the front and worked my way back. I pulled out the wire from then end of the frame near the pivot position. Inside I found a factory harness that was corroded and charred/burned. Everything back of that looked great, so I ran new wire from that point forward. It was then discovered that my 7/4 pin adapter was hosed, then discovered my Main fuse was blown, then found that the secondary fuse was blown.

Whew, check one more off the list.

Thanks for all the suggestions, and Papa Grump for coming over and giving me a big hand!