LED Tail Light Turn Signal - Solved

Pretty stumped on this one so would appreciate any help.

Installed LED tail lights with an integrated reverse light. They work great, the left side is flawless right side is the reason for the post.

The right tail light has an issue with the turn signal. Turn signal works great in stop light mode, it works great with hazards in both stop light and service, but does not flash correctly right side only in service mode. The flash is an extremely weak one you can only barely see when up against the light, another car behind the truck would not see it blink.

Went over wiring several times, flasher unit works great, all other lights work perfectly.

Really confused by this one.

That sounds like a ground issue at the light, with the running lights off the turn/brake signal can find a path to ground through the running light system, once the running (tail, marker etc) lights are turned on that path to ground is gone.

Spent time making sure the grounds were clean and making good contact with the metal crossbar on the back of the light. In the tail light area where would I pull a better ground to verify that's the cause? The part I find most confusing is it works normally in stop light when hazards are on but not in right signal only. I would think the ground path is the same for both those conditions.

Run a wire from the neg lead of the battery to the neg lead of your meter, then connect the red lead to the ground bar on the light and see if you see any voltage there when the turn signal is not working.
Or you could run a temp lead from the neg battery to the ground bar on the light, same thing really.
Just a little less safety without the meter for screw ups.

Did the old lights work before you replaced them? Could be a problem in the blinker switch. When you blink right, you are opening the normal brake / hazard circuit, and routing it through the flasher. Measure your voltage at the light while braking, and while blinking.

You could also just remove the ground from that light's grounding bar and see if the symptoms stay the same, it is possible the defect is in the light fixture itself, if so grounding the ground bar may not have any effect.

Starting to think its an issue with the light fixture. Old tail light had no issue. I grounded with a wire from the negative battery no change. In stop light mode flasher works correctly even when brake pedal pressed. In service mode, hazards make the light flash normally but not when hazards are off and itls just turn signal. Also flashing doesn't work when in service mode when brake is pressed, but that does work in stop light mode.

Have two questions
1. In service mode and I have hazards on, when I press the brake flashing stops on all 4 lights. Is this normal?
2. Does power route through different wires for a tail ight when comparing hazards on vs just turn signal while in service mode.?

Like I said, at this point most likely culprit seems to be the actual light

Yes it is normal for the lights to stop flashing when the brake is depressed, you must be fairly young as all vehicles did that a few decades ago before they separated the turn from the brake lights.

As I said I would remove the ground from that light and see if the symptoms stay the same, I suspect the problem is in that lights grounding circuit, if so you may be able to correct that issue in the light.

I also have no answer as to why it acts differently in hazard compared to turn, I have not gone back and studied the schematics.

No military OE lights have an integral back up. Are these aftermarket? Can you post pics of what you have and more details of the wiring harness?

Mogman - when removing the ground I get no lights. Grounding issue would make sense, but I followed your recomendation and ran a wire from the negative battery terminal and had same issue.

juanprado - Not an OE light, aftermarket with integrated reverse lights so I don't have extra lights attached to bumper. Here's a photo, the wire harness is same as OE lights with the plugs just has an extra lead for the Reverse light. Have one on each side and the left side works flawlessly, the right has the issue.

Azchemwiz said:

Mogman - when removing the ground I get no lights. Grounding issue would make sense, but I followed your recomendation and ran a wire from the negative battery terminal and had same issue.

juanprado - Not an OE light, aftermarket with integrated reverse lights so I don't have extra lights attached to bumper. Here's a photo, the wire harness is same as OE lights with the plugs just has an extra lead for the Reverse light. Have one on each side and the left side works flawlessly, the right has the issue.

Click to expand...

It would only take a few minutes to swap them and see if the problem moves, that would ether confirm or eliminate the lights as the issue.

Good idea, I'll give the swapping a shot when done with work today.

Azchemwiz said:

Mogman - when removing the ground I get no lights. Grounding issue would make sense, but I followed your recomendation and ran a wire from the negative battery terminal and had same issue.

juanprado - Not an OE light, aftermarket with integrated reverse lights so I don't have extra lights attached to bumper. Here's a photo, the wire harness is same as OE lights with the plugs just has an extra lead for the Reverse light. Have one on each side and the left side works flawlessly, the right has the issue.

Click to expand...

Thanks for sharing. There was an OE light with a backup camera similar to that used on the mraps but had a cannon plug instead of the leads but was not a reverse light. They usually sold for a proud price when they come up.... and the controller/screen were rare as hens teeth...
Who is offering those as many here would be tempted? I know I have bought but not gotten around to installing the ambulance style reverse lights.......

I can confirm the issue followed the light fixture when swapped, so I'll have to get that swapped out. Opened it up but the wires go into a sealed compartment where the board is so no accessing anything without destroying the light..

Azchemwiz said:

I can confirm the issue followed the light fixture when swapped, so I'll have to get that swapped out. Opened it up but the wires go into a sealed compartment where the board is so no accessing anything without destroying the light..

Click to expand...

Please let us know where you got them, the cost and how they handle the return

Update, solved the issue and it was not the tail light or the flasher, turn signal handle.

Wound up being a hidden issue with the rear side original LED marker light. During this whole investigation that light worked fine it looked like. Lit up fairly bright, and I only went to replace it today since it was pretty banged/fogged up on the outside and the mounting bolts were rusted. When removing the ground wire it was a bit rusted, but like I said the side light did work so it was grounded. When I did the full replacement it got a brand new ground terminal to replace the old one. And that did it, the right tail light now flashes great in every mode. I never would have thought that the side marker which has a dedicated feed from the wire harness for both positive and ground would have interfered with the dedicated ground of the tail light harness for just the service mode.

Hoping someone that understands the wire harness better than I can explain what I found as it likely will help others.