Trailer lighting problem-need helpor

[bman5150]

A portion of my driver’s side running lights are not working and I’m not having any luck troubleshooting the problem.

Here the wiring on the driver’s side from the connector to the rear most lights on that side:

trailer connector——->first driver’s side running light (works fine)——>second driver’s side running lights (2 lights; they light up the “Triton” logo and they both work fine)——->driver’s side rear lights, which consists of four lights: rear stop lamp; license plate lamp; rear running light and the light bar in the middle of the bottom rear of the trailer.

now here’s the kicker- the driver’s side rear stop lamp is functional. But on the same light, the running light functionality isn’t working. And the other three lights I mentioned in that area don’t work at all.

I cleaned up the ground for three of these four lamps, so I don’t think it’s a grounding issue. I do need to find the ground for that middle rear light bar and see if it’s working properly but I don’t think that would cause a problem with the other three lights that aren’t working. Something is breaking the power that runs the running lamps in between the last one that works on the trailer (the “Triton” logo lights) and the driver’s side rear area running lights.

Am I right in thinking that given the nature of the problem, it very likely has nothing to do with the truck, a fuse on the truck circuit or even the trailer light connector? Would appreciate any help troubleshooting you guys can provide! This is starting to frustrate me!

[CatFan]

Brown wire is probably broken at the last light that works or the first one that doesn’t.

[bman5150]

Thanks. That’s what I’m thinking. I changed out each connector from the last working light all the way back they the rear driver’s side lights that aren’t working. Still nothing. I did discover that my driver’s side “Triton” logo light started flickering when I moved one of the connectors. I replaced that splice connector so at least I averted a potential future issue, ��.

I was was able to move the wires inside the trailer, so it’s not rusted or stuck in one spot as far as I can tell. Seems like I’m going to need to splice in a new portion of wire from the last working light to the rear.

i have a multimeter. How would I be able to use this to identify where the power break is? I wasn’t sure - I’m guessing I’d have to splice / pierce the wire but wasn’t sure where to put the two probes.

[bman5150]

You did give me an idea - I think the first light that doesn’t work is the rear brake light, but only the parking light functionality. The brake light function still works so it’s getting power-it’s just not operating as a perimeter light. That’s what’s really confusing me. Maybe the brake light is a completely different power wire to the light vs the brake light power wire?

[CatFan]

You did give me an idea - I think the first light that doesn’t work is the rear brake light, but only the parking light functionality. The brake light function still works so it’s getting power-it’s just not operating as a perimeter light. That’s what’s really confusing me. Maybe the brake light is a completely different power wire to the light vs the brake light power wire?

Even though they are in the same housing, the brake/TS light is completely separate from the tail light. Brown wire feeds the tail light. Yellow is brake/left turn.

Mist likely failure spot is at one of the lights, and it’s almost certainly between the good marker and the tail light.

[bman5150]

Thank you. Didn’t know that. I wonder if one of my light connectors is just bad? I’ll take another look tomorrow.

but...I know the rear Lower light bar is T’d straight off the brown wire, and it’s also not working. And that’s before it even gets to the other three rear non-working lights. So, it sure seems like I’m not getting power in the brown wire after that last side marker with the Triton logo. It’s as if it’s cut. But from what I can tell, I can’t see where it’s cut.

would it be fine to tap into the hot brown wire that is getting power and just run a new wire back to the rear lights ? It won’t be one continuous wire but I could at least eliminate bad wire from that section.

[billnorman1]

You can tap into the brown anywhere you want to. It's the same all over the trailer, left, right and middle. If you do, do not use a "T-tap" to do so, they let corrosion into the wires and will fail. Temporarily it's O.K., but when you are finished with whatever you use I recommend painting the repair with Liquid Electric Tape.

[bman5150]

Thanks guys. Appreciate your advice.

[Chasman]

Check where the wires come out of the trailer frame for rubbing. You more likely have a bare wire shorting out. Have been blowing fuses?

[bman5150]

Check where the wires come out of the trailer frame for rubbing. You more likely have a bare wire shorting out. Have been blowing fuses?

But some the parking lights on the same line work fine, so I wouldn’t think it’s a bare wire as it would short out the entire circuit, right? I am not blowing any fuses.

[billnorman1]

There are two basic types of wire issues that cause things not to work. Shorts and Opens. Your symptoms indicate an open. An open is where the electricity does not get to where it was intended to go.
Many people call anything that involves defective wiring as a short. Not so in this case.

[bman5150]

Thanks billnorman1. I agree. I think I have one of two possible problems:

1.) electricity is being diverted where it isn't intended to go and away from the rear lights that aren’t working (open) or

2.) there is a break in the wire itself or one of the connectors.

I’m going to keep playing around with it over the next week as I have time but if I can’t figure it out, I’ll be contacting a trailer repair place.

[billnorman1]

You can do it, why pay someone else? And you will be learning. Self sufficiency is always my goal. Just connect all brown wires to each other, somewhere, probably at the last light that works, there is an open connection.

[mrdeath]

I had a similar problem on my trailer and it ended up being a bad tag light. We don't tag trailers in OK, so I just bypassed it and everything worked again. Just something to check.

[bman5150]

Thanks again for all the help guys. Unfortunately, I’m at a dead end. I am sure it’s an open after the last working side logo light. What kills me is I’ve actually cut and reconnected the brown wire where connectors were tapped into that wire, thinking that perhaps the connector cut the wire somewhere due to vibration and corrosion. I did this in two spots aft of the last working light. No dice. I also replaced ever other connector I saw after that last working light-even the ones that tap into the rear light to feed the rear side marker and the license plate light. I’ve replaced all of the lights that are not currently working as well. Finally, I connected the three ground wires for each of the three non-working lights at the driver’s side rear of the trailer (brake light, rear side marker, and license plate light directly to a cleaned up terminal vs sandwiches in with the rubber license plate holder I have. No dice still.

I do have one question: the light bar on the bottom of the trailer does not have a ground wire. The old one didn’t and the new one doesn’t either. It’s just T’d into the brown wire upstream of the rear driver’s side lights that aren’t working. I am assuming that this particular light bar fixture doesn’t require a ground wire because it’s bolted to the trailer (metal on metal). The bolts used to mount it were very corroded but I was able to unscrew the old bolts and reuse them, but I don’t clean them up too well. This is the first light that doesn’t work. It also doesn’t work. Is it possible that I’m not getting a good ground with that light bar, and that’s causing a short somewhere and causing my 3 rear driver’s side lights not to work as well?

sorry for being so long winded. This is the first time I’ve troubleshot my trailer lights to this degree!

[shallowhal]

i had the same issue. could not figure out what was going on. turns out a mouse took residence in the frame and ate the wires. i had to pull new wires down one side of the trailer. its not that bad, really, just put twine on each through frame fitting, pull out the old wire, re-connect the splices for marker lights and pull back through.

light1.jpglight2.jpg

[bman5150]

i had the same issue. could not figure out what was going on. turns out a mouse took residence in the frame and ate the wires. i had to pull new wires down one side of the trailer. its not that bad, really, just put twine on each through frame fitting, pull out the old wire, re-connect the splices for marker lights and pull back through.

light1.jpglight2.jpg

has to be the reason or something like that. The wire is definitely not severed as I can still pull it and move it from both sides.

[bman5150]

If I wanted to try to splice a new wire into that particular stretch, what kind/size wire do I need? Where can I get it?

[billnorman1]

Just remember, unless someone else didn't do a proper job, the wire should be brown. That circuit is the same the whole way around the frame of the trailer, just one big loop. I am a fan of using a test light instead of a meter because it takes current to light a bulb, but a meter just checks voltage.
You can make your own test light with a brake light bulb, and two meter leads. Once you prove the test light works by putting one meter lead on each battery terminal, and the light lights, take it to the trailer and check between ground and the brown wire at each light assembly. An 1157 brake light bulb has 2 terminals on the bottom, hook (solder) one lead to either or both of the solder pieces on the bottom and solder the other lead to the side of the bulb, and once you check it out, wrap it with tape to protect the connection and go to town.

[billnorman1]

I think you use brown 18 Gauge wire, marine grade preferred, copper STRANDED conductors.