Just purchased LED trailer lights to replace my broken lights. When I removed the driver side light the original light has 3 wires coming out of it going to the trailer. The new light only had 2 wires. Not sure how to hook up this side. Other side just had the 2 color coded the same.
What color were the 3 wires from the original light? Brown, yellow and what?
Is there a row of 3 red lights on the center of the trailer at the back?
No center lights. 1 front side marker light on the front, one on each side. Colors were brow and yellow with the third wire being yellow and brown if I remember correctly.
Wires should go brown {running lights} to brown. Turn signals yellow to yellow, green to green. If you have an older vehicle and the turn signals flash quickly. You need to change the flasher. I would also recommend heat shrink connectors or solder and shrink tube.
Yes, connect brown harness to brown light wire and yellow on harness to yellow light wire on new lights.
The only way to know what that 3rd harness wire does is to test it with a test light or multi-meter. If you don’t have a multi-meter, now is a great time to invest in one because believe me, as long as you own a trailer, you’ll need one.
If I had to guess, I would say that the harness marker included a dedicated wire to power either a license plate light or the set of center marker lights, which your trailer doesn’t have. So they knitted it in to a connection on the trailer lights just to cap it off. But that’s a guess. Whatever you do, cap it off with a crimp-on connector or heat shrink tube so that it doesn’t get loose and short.
If you kit came with those evil “Scotch Loc” pinch on connectors that don’t require cutting wires, do not use them. They are the playthings of the devil and they will slowly fail over time and drive you insane. Use proper crimp connectors and throw those POS pinch ons away.
All crimp-on butt connectors on trailer wires must be heat shrink sealed or use heat shrink crimp on connectors. Any butt connector left open will get water inside and corrode and fail eventually. Inspect all frame holes that wires pass through and install rubber grommets on any that don’t have them to protect the wires. Doing this now will save endless time chasing mysterious shorts later.
LED lights can be very ground-sensitive. Some brands of LED lights require a dedicated ground wire to the frame right at the light fixture. Using the trailer harness ground (white) or looping the ground wire to the mounting bolt on the light isn’t enough. Unlike incandescent lights that just get dim with a poor ground, LED lights just don’t work.
If you have a ground by the tongue, put a new loop on it. Use abrasives to clean the spot where it attaches down to bare metal. Re-fasten with a self-tapping screw and then cover the whole area with liquid electrical tape to prevent moisture from getting in and screwing up the ground.
I will have to play with the wires on a warmer day. Have no idea why the stock light had 3 wires in one light and 2 on the other side?
I will have to play with the wires on a warmer day. Have no idea why the stock light had 3 wires in one light and 2 on the other side?
Maybe post a picture of the old light, so we can identify it, and look for a wiring schematic?
HRG
Tried posting a picture, I’ll try again.
IMG_20220221_145913269-scaled.jpg
also post the trailer brand and model.
Then we can look at the wiring diagram online if available
It’s a 1996 top 6×10 utility trailer
And I forgot to say thank you for all that are responding and attempting to help.
the driver side light the original light has 3 wires coming out of it going to the trailer.
Just a guess; The yellow is left turn. The two brown are tailights. (The yellow/brown is just color bleed, just be all brown). The 2nd brown wire feeds the right hand tailight.
Other side just had the 2 color coded the same.
Color code for the passenger side should be one brown and one green.
As mentioned, a multimeter will help you sort things out.
jumperwire.jpg
White-Ground
Brown-Tail/Running Lights
Green-Right Turn/Brake – Remember green has an R in it
Yellow-Left Turn/Brake – Remember yellow has an L in it
If it’s a basic 4 wire and it hasn’t been messed with before. I see a brown yellow, which means you might have some side marker lights on the trailer.
So the right rear light should have a brown and a green wire. The left rear light should have yellow and brown, but I notice in your pic there’s also a brown+yellow wire. I would then suspect there should be a green+brown on the other side.
Do you have pics of the plug end?
Just a guess; The yellow is left turn. The two brown are tailights. (The yellow/brown is just color bleed, just be all brown). The 2nd brown wire feeds the right hand tailight.
In an earlier post, the OP said the trailer does have side marker lights. Of course, the trailer could have the right side marker powered by a wire that ran across the trailer from left marker to right marker. Never seen anything like that but who knows…
My guess earlier was the additional brown wire was to power a set of maker lights you see in the rear/middle of larger trailers. But that is apparently not the case either.
Multimeter or test light time! Figure out what the brown and brown/yellow wire actually does and everything is easy from there. This should not be difficult to figure out, we just need to know what all 3 wires are actually doing.
Ah yes, the never ending headache. It’s 2022 and wired trailer lights are still a thing. What a disappointment
No doubt, wireless trailer lights are available, but then you’ll have people complaining about forgetting to re-charge them,,,,
HRG
The 2 browns are the same wire, one in to the light one out to the next light.
Of course, the trailer could have the right side marker powered by a wire that ran across the trailer from left marker to right marker. Never seen anything like that but who knows…
Had a horse trailer that way. Even the green wire ran down the drivers side, then crossed over at the back (along with the brown). I believe my enclosed trailer is the same, all wires run down the drivers side along the top of the wall. Then cross over to the passenger side above the rear drop down door.
Designers sometimes are strange beings. 
Alrighty then, when I get some warmer weather I will get a test light out and figure out what each wire does. Wished it was as simple as the passenger side. Matched up perfect and working like it should.
Alrighty then, when I get some warmer weather I will get a test light out and figure out what each wire does. Wished it was as simple as the passenger side. Matched up perfect and working like it should.
Well that tells us something. That means the third wire is NOT feeding the passenger side.
Wondering if I have to tie that wire into one of the 2 light wires?
Plug picture
IMG_20220222_131509514-scaled.jpg
John,
I would temporarily wire the new LED light yellow to yellow, brown to brown, hook-up to your tow vehicle, and see what works. If the marker lights on the trailer do not light-up, the yellow/brown(from the trailer) would then be wired to the brown(only) wire.
I wish you were nearby, 5 minutes with a voltmeter and we’d have it all figured out.
HRG
I wish you were nearby, 5 minutes with a voltmeter and we’d have it all figured out.
That’s a big 10-4
That’s the plan, once it’s a little warmer out. Spliced it all together the other day, then realized it wasn’t properly connected. Hopefully it’s simple and I figure it out right away. Thanks again for everyone’s help!
It’s a 1996 top 6×10 utility trailer
How wide is the trailer?I have a 5×10′ trailer and it has the 3-light ID bar,same with my boat trailer.Not sure when it became required to have that on 80″ or wider trailers?
I want to say it’s around 6’6″ wide. Has single side marker lights in the front corners.
Follow up: Took the extra wire off today. Found out lights work perfectly good without it.
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