crazy trailer light problem

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I had a similar problem and it was the ground wire that still was totally enclosed in it’s sheath ,the copper wire inside was totally deteriorated 3 foot in, replaced the whole ground wire from front to back, issue solved.
Sometimes at work we get trucks in with satellite dishes that have the same issue. It loses power and everything looks fine but corrosion creeps down the “weathertite” connections and it’s all chalky and ****** inside. Cut out the corrosion or replace the wire and problem solved. I just did one a couple weeks ago. I think it was only like 2-3 years old.
 
Got a head scratcher with my trailer lights. My tag along trailer I use to haul everything set unused for 2 years. It was loaded down with metal building studs and I just got around to selling them a few weeks ago. The taillights where broken and not working so I bought new lights and installed. Hooked trailer to truck and no lights worked. Well my first thoughts was corrosion in the plug or bad ground. I took the pigtail apart, cleaned all the wires and tested the lights using a battery charge, everything worked. OK plugged it into truck and nothing worked. So next was pull out the meter and check outlet, everything seemed to be working but it was crusty so I took the outlet apart, cleaned all the wire ends and reinstalled. Meter said everything worked. Plugged it all back together and still no trailer lights. Almost automatically thought bad ground so I took my meter and did a continuity check between the outlet and the trailer, meter beeps so ground is working. I tried bumping the plug in to make sure it was getting contact, wiggled and pulled on the plug, nothing. Well crap, sometimes I have had trailer lights not work until the trailer was pulled cleaning up the ball and coupling making a ground and then the lights would work. Not this time. I loaded my tractor and pulled the trailer about 5 or 6 miles and back, still no lights. What am I missing.
Missing? A new wiring harness from the 4-flat to the lites, which is about 20 bucks....and remove the lites from the mount and clean that surface as it serves a a ground....Trailer wiring isn't rocket science, nor something deserved of all the time spent sending this post?
 
If the tow vehicle was built after '06 (Manufacturing quality of all brands took a nosedive for '07, especially with GM), check the vehicle for power first. If that checks out, concentrate on the trailer.

If you've got power at the sockets, then the bulbs are bad, or you've got extremely chinese lamp assemblies. I've seen corroded sockets prevent a good ground, and I've also seen dual-filament bulbs short across the brake/tail to running lamp circuits via a blown filament. I've seen chinese assemblies that had bad grounds internally, and poor contact due to loose and extremely cheap sockets. I've also seen bulbs that visually looked 100%, but had an open circuit somewhere inside the light that was NOT the filament.

Short circuits are extremely common in all wiring, especially when trailer manufacturers run wiring through washers welded to the frame (Dively) with zero protection for the wire.

In the Northeast and anywhere else road salt is used through the winter, corrosion of literally EVERYTHING is an issue, especially connectors, plugs, sockets, or any break in the wiring insulation.

Voltage drop testing is your friend. Plenty of YouTube vids on the subject. Anything more than 1/4 (.25) volt can cause issues. On LED lights, I'd want to see no more than 0.10v drop. A volt or more is definitely causing issues. If your meter reads 12v, that means there's a 12v drop ... AKA, ZERO volts. Good luck!
 
Well thought I would just stop in and say I found the problem. It was the ground from plug to trailer frame. I had forgot I had mounted a stud for a ground wire inside the trailer tongue, The bolt was very rusty. I also have another ground bond at the back of the trailer which is what I was concentrating on as being the problem. Took it off and cleaned and just like magic, the lights turned on. Of course I forgot to turn off the switch on the truck so the next day my truck battery was dead, but the lights work. Next I have to install a brake box in the truck. Should be easy enough, the truck has the tow package and is prewired for a box, so plug and play.
 
Always use Self-Sealing or Heat Shrink Splices. Open end splices will eventually corrode and fail.
I used to work at a truck building facility that built FedEx/UPS trucks among many others. They banned using scotch locks when they had to replace instrument clusters and wiring harnesses on the trucks. Water migrated from the rear of the truck forward to the IP through the wires when they used scotch locks to splice in the trailer plug when they added a receiver to some of the trucks. Heat shrink/solder heat shrink connectors were the only things allowed after that.
 
The thread says, you are scratching your butt about trailer lites 101. I just thought I'd share the laugh found in that.
To be honest, I posted just to have something to discuss. I knew I could figure out the problem without help, but posting about it might help someone else with a similar problem,. I have built and wired many a trailer, had to rewire many a trailer and I am generally pretty good at trouble shooting light problems. I said from the get go that I thought it was a ground problem. I also posted that I had installed new lights, cleaned all contact surfaces and took the plug and receptical apart and cleaned and reassembled. I think I pretty much covered trailer lites 101. When I originally built this trailer, which was probably 15 years ago, I ran a ground wire all the way to each light. the problem was that I also bonded the ground wire on the trailer tongue. The bond stud is mounted below the electrical junction box so without actually bending over and looking under the box, you wont see it. I had forgotten about that bonding point and just assumed the ground wire to the lights was one continuous wire. When I removed the wire from the stud and hit the wire ends and stud surface with a piece of sandpaper, the lights begin to work. Nothing dramatic and no need for dramatics.
 
You have to realize that when you post something on a site like this, people generally assume honesty and take you at your word and try to help. I just went back and read your original post, and like others I now am left with one question: was he lying then or is he lying now? This last post and the first one, if I take them both honestly, are incompatible. What should I think now?

You will leave a lot of people with the impression that you just treated them like chumps for responding to your first posting; a few of them even got into verbal spats with each other over it. Was this wise?

The discussion may have run more smoothly had you posted the problem in the start as a hypothetical question instead of a real puzzle you couldn't solve.
 
You have to realize that when you post something on a site like this, people generally assume honesty and take you at your word and try to help. I just went back and read your original post, and like others I now am left with one question: was he lying then or is he lying now? This last post and the first one, if I take them both honestly, are incompatible. What should I think now?

You will leave a lot of people with the impression that you just treated them like chumps for responding to your first posting; a few of them even got into verbal spats with each other over it. Was this wise?

The discussion may have run more smoothly had you posted the problem in the start as a hypothetical question instead of a real puzzle you couldn't solve.
And just what part of my post do you think is a lie. I posted what I thought the problem was and what I did to check for the problem. I then followed up with what I found the problem to be and what I did to correct the problem. Why would you call any of it a lie? To ask for help solving a problem, even knowing I could most likely solve the problem with out any such help, is not lying, and it does serve as a learning tool in the event someone else is having a similar problem. Asking the question and the responses given just verified what I thought I already knew. Lots of good advice was given and worth reading to anyone having trailer light problems and maybe doesnt have the knowledge to troubleshoot the problem themselfs. Sure, not everyone agreed on the best electrical testing method, but I didnt see anyone about to come to blows because of it.
 
Fair enough, it's an honest question. And accept that I'm not at all being nasty, I'm just proposing something that might have made the discussion better. You are correct that it prompted a lot of good advice.

Where I see the lie is by your last post that I reacted to, you say you are completely conversant with trailer lighting, have built many trailers and wired them and were perfectly capable of solving any problems; that you actually needed no advice. Conversely, in your first post you said that a beep on a continuity tester proved good ground; it does not and you knew that at the time--plus in the later post you disclosed that the problem was...a bad ground. You said in the initial post that you have got lights to work in the past by driving enough that ground was established through the trailer ball and socket; you also then by the later post know full well that that is not a proper or reliable ground.

The last part of the original post of driving 5 or 6 miles implied that you then went out on the road towing a trailer that you knew had no lights. To a professional driver that one stands out like a sore thumb; who would do that?

So the lie is in presenting yourself first as someone relatively clueless with trailer lights, and then disclosing that you were actually completely experienced with them. Can you see that someone thousands of miles away has to see one of those two as a lie? The lie is not in anything technical about the wiring or trouble-shooting; it was in the way you presented your ability. Next time I see a posting like your original one, what will my reaction be?--probably to ignore it because the last time I was had; the poster in the end didn't need any of my advice at all.

I understand what you were trying to do, but you must be aware that these forums can be volatile places; even following this discussion a few people started jousting with each other. But people will react according to what they perceive your ability to be, and you misled them in the first post if the later one is honest. I'll accept the later one; you know what you're doing.

I should offer what I'd have done in trying to achieve your intended goal--like presenting the same scenario as a friend having the problem you outline, and ask what advice people would give to him. At least state up front what the goal is rather than presenting yourself as something you are not if you are way more knowledgeable than you presented yourself as being.
 
Fair enough, it's an honest question. And accept that I'm not at all being nasty, I'm just proposing something that might have made the discussion better. You are correct that it prompted a lot of good advice.

Where I see the lie is by your last post that I reacted to, you say you are completely conversant with trailer lighting, have built many trailers and wired them and were perfectly capable of solving any problems; that you actually needed no advice. Conversely, in your first post you said that a beep on a continuity tester proved good ground; it does not and you knew that at the time--plus in the later post you disclosed that the problem was...a bad ground. You said in the initial post that you have got lights to work in the past by driving enough that ground was established through the trailer ball and socket; you also then by the later post know full well that that is not a proper or reliable ground.

The last part of the original post of driving 5 or 6 miles implied that you then went out on the road towing a trailer that you knew had no lights. To a professional driver that one stands out like a sore thumb; who would do that?

So the lie is in presenting yourself first as someone relatively clueless with trailer lights, and then disclosing that you were actually completely experienced with them. Can you see that someone thousands of miles away has to see one of those two as a lie? The lie is not in anything technical about the wiring or trouble-shooting; it was in the way you presented your ability. Next time I see a posting like your original one, what will my reaction be?--probably to ignore it because the last time I was had; the poster in the end didn't need any of my advice at all.

I understand what you were trying to do, but you must be aware that these forums can be volatile places; even following this discussion a few people started jousting with each other. But people will react according to what they perceive your ability to be, and you misled them in the first post if the later one is honest. I'll accept the later one; you know what you're doing.

I should offer what I'd have done in trying to achieve your intended goal--like presenting the same scenario as a friend having the problem you outline, and ask what advice people would give to him. At least state up front what the goal is rather than presenting yourself as something you are not if you are way more knowledgeable than you presented yourself as being.
Well, you posted your opinion and I have posted mine. I would have thought that someone that has worked on as many trailer lights as you claim would have read my first post and realized I had already checked the basics and had taken corrective action as to any possible problems. Nobody knows it all, and nobody likes a know it all. I will just agree to disagree and let it go at that.
 
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