Trailer lights fuse

[Fergie]

2012 Pete 386 with 2010 Wilson grain trailer
Keep blowing fuses for my trailer clearance lights. Still have turn and brake lights. Don't use lights much, third fuse in about 3000 miles. This last fuse lasted 10 minutes. Replaced 2 side markers with bad lenses was told moisture on LED could be my issue. Got to replace one more light that's out(maybe my issue?). Put a new plug on trailer. Where do I start to find my issue.

[Fergie]

Just replaced fuse and it blew 5 minutes later.

[Rawze]

You try a different pigtail?

NOt sure about what you got, but we haslte with our share of worn out dry/reefer trailers. We have seen our share of shorted out marker light wiring at the top of the trailer near where the doors close. Slamming a door shut will often make the beaker in our dash pop and we have to reset it.

[Fergie]

(10-16-2017 )Rawze Wrote:  You try a different pigtail?

NOt sure about what you got, but we haslte with our share of worn out dry/reefer trailers. We have seen our share of shorted out marker light wiring at the top of the trailer near where the doors close. Slamming a door shut will often make the beaker in our dash pop and we have to reset it.

No on pigtail, put a new end on it also. Can swap one out in the morning. If one bulb on an led light cause a short like this? Saw I had another one with a bulb out. Never had an issue with this with my previous truck pre June and while I was waiting to remove mandate I had it on another older truck and no issues in a week in August. I thought maybe bouncing down the road did it but this last fuse blew while I was parked and getting loaded. Could a relay be doing this? This is a 30 amp mini fuse that's blowing. I'm thinking it's in the truck.

[Fergie]

Wanted to run tonight but couldn't. Replaced 2 bad amber lights on trailer, blew fuse right away. Had time in the field waiting to load so crawled under truck, that's where peterbilt told me to start. From the computer in the frame by the transmission a foot back was a connector they told me that gives fits. I was tired of laying on bean stubble so I crawled out got loaded and drove the mile to dad's place and got it on cement. Pulled 2 tail lights connection still good. Crawled into the nose and that wiring all looked fine. Went back under truck and went to that plug by computer unhooked it and put it back together. Didn't work on it much cause I'm not familiar with this type of plug. Was told it's a coupler. Had a wire or two come out of it. Out of fear of f-ing more of it up I put it back together. Went to turn lights on to show dad how fast it was blowing the fuse and the damn thing stayed working. So I'll be getting a new coupler ordered tomorrow and hoping whatever I fiddled with can last till a rainy spell. A local farm mechanic I've been bouncing ideas with said if it kicks out again he'll bypass and tie into my truck lights just to get me by. Whether that'll do it with this new crap IDK. Hoping things go good for once tomorrow had to shut down yesterday for a cam shaft sensor that our local dealership didn't stock and didn't get till noon today.[/u]

[dhirocz]

Try the wiggle test. Put a new fuse in it, turn them on, the start wiggling the wires around from behind the trailer connector all the way to the lights. While wiggling, look for anything that might look like it could cause an intermittent short while driving.

Have you checked the circuit with a multimeter?

My tractor did this...I had a broken wire going in to the trailer electrical socket behind the cab.

[Rawze]

With a short like that, as a last resort, I use my el-cheapo 75-amp battery charger with it set on trickle charge (10 amps), it going through a couple of cheap-o 100-ft spools of #12 wire from the hardware store on the circuit with no fuse (to limit the current even more). An old 100-ft drop cord works instead of a spool of wire too. - After wrangling on sh?#it and trying to find the intermittent connection for about 3-5 minutes, I can usually follow and see the wire slightly warm all the way to the short using my thermal camera.

[the missing link]

Great idea I have done the same , just a different way .
On my trucks and trailers I have had the same thing after hotwireing it I blew a light , and that was the problem . I have had that happening a few times . A lot of poeple say that can't happening , but it can .
I bought a brand new truck , 10000 Kms on it and I could not keep marker lights on , blowing fuses . I told the dealership , " well it could take all day to find it " . I got pissed off threw a 20 amp instead of a 10 amp in . I know I should not do that , but I did ... 1 min later a marker on the fender brunt out and it never blew anther fuse .
Can't be in the light eh , oh we have never seen that happing before ! Yeah ok
Led or bulb , it can happing .
Note to anyone don't ever buy a mopar 5 th or factory mounts !
I won't get into the story of a 2015 3500 cummins that is unsafe to pull a 5 th wheel trailer, with a factory mounts and hitch ....
I would love to see those f$ckers burn !
Rant over for now, lol

[Fergie]

Let truck warm up in shed with lights on for about 15 minutes, pulled out of shed made a slight turn lights dimmed came back to full power and then blew. Put new fuse in and it made it a mile and blew. Threw hazards on and decided to go the 6 miles of country roads to a town where I figured I'd sit till light out. Pit fuse in on main Street drove 5 blocks to the gas station and they stayed on while going to get coffee. Starting to get light out so I left figuring I'd cut threw the country. They stayed on for 15 miles then blew. It was light enough where I could keep going. Sitting in line now and doing some digging. It's not just trailer lights going out. It's taking all clearance lights except for the roof lights. Never noticed before cause I never checked them I only looked up at the cab lights. I guess a blond moment. Right now I unplugged the trailer and got lights on. Been on for about 15 minutes and hasn't blown yet. Going to pick up a new relay to try. I have a bad feeling this could be hard to find.