Tail light problem

[Scott H]

So my tail lights don't work. They are newer LED's. The lights themselves work; brake, turn signals, no problem. It's just the running lights.
I have a snowmobile/raft trailer that connects via 4 pin (the Trillium is on a 7 pin), same problem. Just had all the wireing professionally redone on the trailer.
So it's gotta be my tug right? Checked fuses, visually inspected wireing as far as I could. Whats next? Take it to a pro? Just run a new wire? advise?

[mszabo]

Tow Ready® 20117 - 7-Way Flat Pin Car End Tester with LED Display

I use a tester similar to this one. This way I know if it's the trailer or tug.

[The Minimalist]

Do you have a 7/4 way connector on the tow, or are you using a 7 way to 4 way adapter for the raft trailer?

[Carol H]

Pick up a tester and check for power from the tug on the running light wire. If no power check for an corrosion on the plug - in particular take a look at the running light wire where it connects in at the back on the tug side - it could also be that the screw holding the wire in is loose. If you have power on the tug side then check your trailer plug for corrosion and clean it up.

[C&G in FL]

What is the tow vehicle? Does the vehicle have a factory installed "tow package?" I had the same problem with my F150. It was a fuse in the distribution box under the hood, not in the fuse box within the cab. I actually read the description of each fuse in the owner's manual three times before I determined which fuse it was, because the fuse description was somewhat misleading. I spent a lot of time testing and checking as Carol suggests. Then found out it was something simple, at least in my case.


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[Byron Kinnaman]

Originally Posted by mszabo

Tow Ready® 20117 - 7-Way Flat Pin Car End Tester with LED Display

I use a tester similar to this one. This way I know if it's the trailer or tug.

You can get one of those, but you'll also need one of these
If got the Multimeter you could use it instead of "Car End Tester" plus any other electrical problem you might was check.

[Scott H]

Thanks for the advise. Guess I've got to get a tester. To be clear, I have separate 4 and 7 pin connectors on the tug (2002 Tacoma) for the two trailers. Same problem with both. I've checked and rechecked the fuses under the hood.

[Carol H]

Originally Posted by Scott H

Thanks for the advise. Guess I've got to get a tester. To be clear, I have separate 4 and 7 pin connectors on the tug (2002 Tacoma) for the two trailers. Same problem with both. I've checked and rechecked the fuses under the hood.

If after testing it turns out its on the truck side you might want to check to see if your wiring harness on your truck has a small little electrical modular box with a few lights on it. Sorry not sure of the correct name for the little box but I have heard it called converter a few times ? May be buried behind a taillight lens perhaps? Looking on etrailer at the harness they sell for your truck there appears to be one. I had one on the after market wiring harness on my last tug that failed after a few years that resulted in only some of my light functions working correctly.

[Byron Kinnaman]

Originally Posted by Carol H

If after testing it turns out its on the truck side you might want to check to see if your wiring harness on your truck has a small little electrical modular box with a few lights on it. Sorry not sure of the correct name for the little box but I have heard it called converter a few times ? May be buried behind a taillight lens perhaps? Looking on etrailer at the harness they sell for your truck there appears to be one. I had one on the after market wiring harness on my last tug that failed after a few years that resulted in only some of my light functions working correctly.

What I think you're talking about probably doesn't apply or is ok in this case. It's a converter to convert from some vehicles that have separate turn signal light and brake lights. The trailer lights are the same lights for both brake and turn signal. Scott indicated that brakes and turn signal light work just fine. So I don't think that brake/turn signal light converter, if there is one, would be the problem.

Since he claims that he just had a "professional" rewire the trailer, if it was me I take the tug and trailer to the guy that did the wiring and have him fix it. If it worked before the rewiring he did something wrong.

[C&G in FL]

Since the OP has stated that he is having the same problem with 2 trailers, it is most likely a problem with the tug. It is unclear from the post whether the Trillium or the snowmobile trailer was "professionally rewired," or even if the running lights were working properly before the "professional" did the rewiring. Did the OP tow the trailer to the professional with the lights working or was it rewired because nothing worked? Did the "professional" have access to the tug or only the trailer? Also, how old is the tug? Corrosion usually doesn't form overnight.
All the suggestions made here are valid, but all are "shots in the dark." Any non hands-on diagnosis is more likely to be accurate when based on detailed information. So Scott, tow vehicle make? Do you know if the running lights were working on either trailer before the rewiring job? What do you mean by professionally rewired? More details, please.


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[Terry G]

Uh, this might be something very simple. Although older incandescent bulbs will work with the wires connected either direction, LED's are polarized and the positive and negative wires must be connected correctly. (I'm assuming the running lights are also LED.) It's a longshot, but definitely worth a check. And i would strongly suggest a multimeter rather than just a probe when you're trying to figure out trailer wiring.

[steve dunham]

Take a source of 12 VDC and connect the 12 VDC POS+ to pin #3 (Brown wire) and the 12 VDC NEG - to pin # 1 (white wire) on the trailer plug in connector.Then see if your trailer running lights are working . If the trailer running lights work then the problem is in the tow . I would suspect the problem is in the TV but by testing the trailer you have solved for part of the equation

[Scott H]

Thanks again for all the responses. Kinda fun trying to solve a puzzle via the internet that is ultimately insolvable unless you are hands on.
Here's some more clues:
To clarify the tug is a 2002 Tacoma, no factory tow package, but I bought it with a 2" receiver and a flat 4 connector. When I replaced the axel on the Trillium about 5yrs. ago I added brakes and hence had them wire in a 7pin connection in addition to the flat 4. Worked perfect. Installed new LED tail lights, wired them backwards, figured it out, fixed it, and they worked perfectly for a couple years. Noticed that the raft trailer's tail lights weren't working, but brake and turn signals were. It was an inaccessible, rusted mess. Took it in and had it rewired (no tug). Assumed it was fine (and it works perfectly when towed by a buddy's truck). Last fall I noticed that the trillium's tail lights weren't working. Replaced both the male and female 7 pin connectors to no avail.
Now I just tow during the day light.
Living in the desert SW, corrosion is virtually non existent.

[C&G in FL]

Given that information, if the running lights on the Tacoma work, and neither the 7-Pin or the 4-Pin connector provide running lights, trace that conductor back to where it was wired in. Could be bad splice feeding that pin on the connectors. If the Tacoma came from factory with the 4-Pin connector and it wasn't wired in by the previous owner(s), I would still look at the owner's manual and carefully read the description for each fuse. I believe there is a power distribution box under the hood in a Taco with some fuses and relays. Check there.


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