73-87 Chevy _ GMC Trucks > Electrical

Rear LED Taillights are trashed


Sometimes I think I've got dimentia. Bought these expensive United Pacific rear LED Taillights. Read and re-read the directions. The loose yellow wire and the explanation confused the heck out of me. I bench tested them. For some reason, I thought I had to swap the red and yellow wires.  I seemed to think the sequential light was a function of the red wire, not the yellow. Sequential is the switch on the back. I even made a video of the light on the bench. The directions are long gone since my bench test worked.


I just found at least three videos on YouTube that clearly say just plug the Stinking cable in. But no, I was so danged confused, I swapped the red and yellow wires. It must be dimentia...

But everything was cool. Everything seemed to work. But it's not. The flashers work, the parking light works, but when you turn them both on, all I get is solid. Put the red back where it's supposed to be, yellow is hanging. Both left and right sides are bad. Equal opportunity destruction. Replacements all backorder unless I buy the lights without the trim and be different front to back.

Searching more on the web, the explanation for the yellow says if you want full on, connect that to a seperate switch off the brake.

Now I'm really confused. If the red wire flashes and I've got a seperate brake wire switch run to the yellow as the directions say, when the flasher is off, that's the same as my swapping the wires. The yellow will be lit up when the brake is on and the red goes on and off with the flasher.  How would that ever trash the LED?? It makes no sense. It's like I somehow blew a diode, but that's normal operation for the yellow wire.

I'm about ready to just throw this whole business away, buy some old plastic sets, they're much cheaper, and some led 1157 off Amazon like I did for the front.

Maybe I start poking through the conformal coating looking for the blown diode.

Any suggestions?

Sounds like you just hooked them up wrong. Email the company and ask for help

Ahhhhh, I got them to work as a standby, will call UP tomorrow.  I've learned two lessons from this...

1)  When confused, always, always search for youtube videos.
2)  Use the desktop for a search, not the phone search.

I found in a different forum, exactly the same issue.  They solved it by getting a flasher provided by UnitedPacific.

Turns out I am not fully senile.  When I put this together, I had regular bulbs in the front flashers.  Everything worked beautifully.  The issue came in when I replaced the front bulb with LEDs.

I put the regular bulb back in and viola all is working properly again.  I switched back from the yellow wire to the red wire, operates the same either way.  At least it's all good again.

I'll ask them what's different about their flasher that the regular LED flasher doesn't work.  If I'm not satisfied, I'll just keep using the regular bulb.


Ok, it's all figured out...

The rear taillights need the voltage to drop to a level before they'll flick off.  There's not enough load to draw down the voltage with the LED flasher i'm using.  My digital multi-meter doesn't do a great job, but you can see the voltage go up and down.  (Now i wish i had one of those simple oscopes you can plug into the USB of a laptop to see the waveform).  Three scenarios...

1) Incandescent in front - measured lows, meter says between 0.02 and 1.2V for a low.  Works.
2) LED in front, no parking lights - low about 2V.  Works
3) LED in front, parking lights on - low about 2.5V.  Doesn't work.
2) No bulb in front - Low about 2.2V.  Doesn't work.

So the low needs to drop around 2V for it to work.  It needs to be much lower.

The flasher I bought from autoparts store is fully electronic.  It should have super long life.  UP has a flasher that runs a relay.  The guy says with the relay we'll get the voltage to drop down to where it needs to.  I'll experiment and see how low it goes.  I ordered p/n 90652; 90649 was listed, but sold out.  he said either one will work, they're the same.  I ordered 2, one for the turn, one for the 4-way hazards.


I also debugged my issues with my hazards.  They just didn't do anything.  First off, the wiring harness comes with two flashers, but the box only has one mounting space and no mention of what to do with the second flasher.  That's the hazard flasher.  It needs to be added in-line to the wire.  On top of this, there's no power coming from that wire in the fuse box.  I'll need to take that box off to figure out why there's no power.  The fuse is fine and you can measure power on both sides.  I guess a few more checks before i take that box out, not something I look forward to.  That was supposed to be done!


Doh! The hazard flasher is upper left corner, just not molded circle like the turn signal lower right.

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