Led Stop/Tail lamps flashing issue

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Hey all,

Had to pull off the road last night, turned on the hazards, and noticed the tail lamps were flashing along with the turn signals. After playing around with different scenarios this morning, looks like:

- Lights off, turn signal works normally, tail lamp off
- Lights off, foot on brake, turn signal works normally, tail lamp works normally
- Lights on, turn signal causes red tail lamp to flash along with it
- Lights on, foot on brake, turn signal works normally, tail lamp works normally, no flashing.
The flashing tail lamps occur with either turn signal or both with the hazard switch.

I have LEDs from superbright installed in the tail socket and reverse socket...anyone have a quick idea before I tear into the side panels and wiring harness this weekend?

Here’s a quick five second video:

 
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You have me supremely curious, I will be staring at wiring diagrams while I drink my happy hour beer because off hand this makes no sense...

Clark
 

OSS

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Put the incandescent bulbs back in the lights and try again. If they work fine with the regular ole incandescent bulbs, the culprit is the LED bulbs. Some mess with things.
I know that the Cree high intensity led backup bulbs caused no problems. Definitely LEDs in the turn signal bulbs usually cause problems
 
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After a couple sips of beer, I have some thoughts. They should be completely independent systems with the exception of the switches being colocated on the steering column. This seems like the mostly likely place for a short between the two systems. Not sure if that column switch can be taken apart or not? Typically, the LED issues revolve around the fact that LED's don't draw enough amperage and so the flasher blinks twice as fast, as if you had a burnt out bulb, but I'v hard of some odd ball things with LED's and 60's, given the switched ground on the headlights (nothing like this though).

Clark
 
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Turn signal bulbs are regular incandescents, no led modifications there...

Put the old bulbs back in and whatdya know, no funny flashing. If I get reaaaaal close to the lens I can see the tail bulb pulse a little, it must be enough of a current to kick the LED bulbs on full power. Even with a regular bulb in one socket and an LED in the other the flashing doesn’t occur with the LED bulb.


Regular bulb on the left, Led right:

Both old regular bulbs, back to normal:

I’ll add this investigation to the to-do list (‘cause I’m curious why there’s a pulse on the tail lamp wires) and tackle it later on.
 
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My friend also had some issues with rear lights. We opened the rear driver's side quarter panel and down in there someone had made a real mess to tie in trailer lights.

Look for odd home brew wiring in the rear. If that is not the case then I agree with midknightc3 that it may be in the column although unlikely.
 
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@aviafx did you ever get this worked out? I have the same issue while utilizing LED's for my brake, tail, and blinkers so would be curious if you made any progress.

Cheers
 
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@aviafx did you ever get this worked out? I have the same issue while utilizing LED's for my brake, tail, and blinkers so would be curious if you made any progress.

Cheers
No dice, the ol’ 2F started knocking last spring (time for a new motor) and I haven’t revisited the issue. Good luck!
 
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I have same issue and there's a relay replacement from Superbright LEDs (I got mine there too)...what I'm trying to find now is the blinker/flasher replay location. Chilton's isn't helpful. If anyone knows that we'll be set.
 
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So have I have a similar issue. I had an issue with the trailer wiring and ripped that out and solved some issues. But, I’m having issues again. What I think might be causing this is that the rear lights share a common ground. I think the LED don’t cause enough voltage drop and the they are back feeding the other light through the ground. Just my theory and I also don’t know what to do about it. Lol
 

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So have I have a similar issue. I had an issue with the trailer wiring and ripped that out and solved some issues. But, I’m having issues again. What I think might be causing this is that the rear lights share a common ground. I think the LED don’t cause enough voltage drop and the they are back feeding the other light through the ground. Just my theory and I also don’t know what to do about it. Lol
I think in our case I believe the hot is the shared lead and the ground is what's switched. I'd have to double check my FSM but if that is the case, there could be another problem in the wiring causing the LEDs to flash like they are. If your trailer wiring has been removed that eliminates one problem. The circuit is (however briefly) being closed somewhere in time with the blinkers, so I suspect there's a chafed wire or messed up connection somewhere.
 
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I think in our case I believe the hot is the shared lead and the ground is what's switched. I'd have to double check my FSM but if that is the case, there could be another problem in the wiring causing the LEDs to flash like they are. If your trailer wiring has been removed that eliminates one problem. The circuit is (however briefly) being closed somewhere in time with the blinkers, so I suspect there's a chafed wire or messed up connection somewhere.

The rear lights are positive switch. The each bulb assembly has a white/black wire that all comes together into one and is ground nearby. At least that's how it is on my '88. The issue I have is that I'm getting a small amount of voltage to the reverse lights, not enough to light them up, but enough to trigger my head unit to make it think it needs to display the reverse camera. Also, depending on the day the left hand turn dash indicator will be dimly illuminated once the lights are turned on. Combine that with, if the lights aren't on or if for some random reason the head unit isn't being triggered, if I step on the brakes the head unit get the reverse camera trigger. I know the voltage is low, because it's never enough to actually power the reverse camera. Like I said before this is probably a common issue that is masked with the high resistance of the normal incandescent bulbs. I really think since the LED use so little wattage the rest of the bulbs in the tail light assembly are getting back feed from the ground.

For what it's worth, I have a friend locally that has parted up a lot of 60's/62's. I'm going to swap assemblies with him for one that's not all nicked up from having splice connectors on it.

The diagram doesn't really do a good job at showing how the ground is set up. I'll try to grab a photo when it's not raining and dark out.

rear lights.png
 
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Alright I lied, the rain let up and I went out there to take some pics.
I also turned the lights on the tested the voltage from the outside(ground) of the brake lights to the ground bolt by the washer bag.
0.026 volts with just the lights on
0.056 volts with the brake applied

You can see in the pics I've tried fixing this before. Wrapped where they had the quick splices installed with electrical tape, even cut and re-spliced some wires. Even put electrical tape around the connector for the ground wires thinking it might have been contacting something.

IMG_0696.jpg

IMG_0697.jpg
 

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Alright I lied, the rain let up and I went out there to take some pics.
I also turned the lights on the tested the voltage from the outside(ground) of the brake lights to the ground bolt by the washer bag.
0.026 volts with just the lights on
0.056 volts with the brake applied

You can see in the pics I've tried fixing this before. Wrapped where they had the quick splices installed with electrical tape, even cut and re-spliced some wires. Even put electrical tape around the connector for the ground wires thinking it might have been contacting something.

View attachment 2496532
View attachment 2496531
If you can take them in to a bench, I would solder and shrink wrap each splice to make sure they're completely isolated from each other and there isn't any resistance in the splices to cause back feeding of power (believe it or not that can sometimes cause issues in sensitive circuits).
 
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If you can take them in to a bench, I would solder and shrink wrap each splice to make sure they're completely isolated from each other and there isn't any resistance in the splices to cause back feeding of power (believe it or not that can sometimes cause issues in sensitive circuits).

Like I said I'm just going to swap it. Buddy has a bunch of them. He said no one ever buys the assembly, just lenses with is funny cause you can still find those new and the ones he has are almost always cracked.... I'll try to remember to report back if that fixes the issue.
 
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For what it's worth, those heat shrink self-solder butt splice connectors that you can see on the bottom sockets are money. I was super doubtful they'd work, but they quickly have because my favorite thing for splices like that.
 

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