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LED Brake and Turn Signals, brake lights illuminate both turn signals

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Old May 15, 2016 | 07:41 PM
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investinwaffles's Avatar
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From: Tarpon Springs, FL / Denver, CO
Year: '98
Engine: 4.0 I6
Default LED Brake and Turn Signals, brake lights illuminate both turn signals

Ok, new one for me that I seriously can't figure out

I recently installed LED turn signals and brake lights (Sylvania Zevo LED's). I also installed a Novita EP27 Electronic Flasher which eliminated the hyper flash condition.

I am having another issue that I haven't been able to fix, which is that when the car is running, activating the brake lights ALSO illuminates the turn signal LEDs but just barely.

I verified that this is happening with the OEM flasher, and I did try to mess with the contacts of the 3157 (dual "filament") turn signal bulbs, but can't get them to stop lighting up no matter what I tried. I bent the contacts back to normal but the socket itself is a 3156 single filament socket so it only makes contact with the 2 primary pins anyways

It is the primary diode that is illuminating, but not to full brightness (I estimate +- 5v), and activating the turn signal causes the bulb to operate normally (meaning turning completely off and going to full brightness during its flash), though the other turn signal will stay illuminated.

This is ONLY happening when the brakes are applied, and the car is running. Its some sort of residual voltage that is on the turn signal circuit, which isn't enough to light up the incandescent bulbs but which is enough to barely light up the LED replacement bulbs.

Does anyone know how I can fix this? I really like the LED turn signals, but obliviously it looks really weird to have the turn signals illuminate slightly when braking....

Would some sort of load resistors help, to eat up the residual voltage on the circuit?
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Old May 16, 2016 | 03:03 PM
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From: Tarpon Springs, FL / Denver, CO
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Anyone have any ideas? I guess I will order some resistors and find out myself
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Old May 16, 2016 | 03:50 PM
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Had the same problem, tried many combinations of resistors and just went back to stock brake lights and it will only do it now when I use my hazards.
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Old May 23, 2016 | 02:38 AM
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Thanks for the advice

I returned the LED turn signals and swapped incandescent bulbs back in. With the LED brake lights, everything is totally fine - the incandescents don't light up at all.

I will update this thread if I ever find out what is causing it, and how to fix it.
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Old May 25, 2016 | 09:28 PM
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When going to LED you usually need to individually ground each LED taillight by itself instead of relying on the factory harness. This has fixed issues before, but I have never tried it on a Cherokee.
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Old May 26, 2016 | 01:29 PM
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Originally Posted by trans_am7935
When going to LED you usually need to individually ground each LED taillight by itself instead of relying on the factory harness. This has fixed issues before, but I have never tried it on a Cherokee.
I'll have to try that because I can't get these stupid lights of mine to work right. I have no clue who the parking lights and turn signals all go to crap. I forget if it's any time I have LEDs in the brake lights or anytime I don't have resistors on all 4 corners for the turn signals. I think it's just when LEDs are in the brake lights or I wouldn't have taken them out I guess.
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Old Aug 29, 2017 | 01:53 PM
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I'm gonna go ahead and raise this onefrom the dead. I've been challenged to figure out exterior LED signal lights and the suggestions in this thread are interesting. I'm going to put some to use and see what happens.

I've got a couple issues that I've not been able to resolve, although I've not exhausted testing just yet.

1. The dash turn inidicators glow when driving/marker lights or the headlights are activated. I have LED instrument lights, so I could replace the instrument turn indicators with stock bulbs or try grounding brake/turn lights individually.

2. Any problem (putting a singal 'filament' LED in a double 'filament' spot can mess up the entire process.

3. When I put any type of high power LED in the front marker light area, the entire turn process fails.

Intermediate conclusion: LED Turn signals are a pain and likely not worth the trouble. LED brake and backup lights work easily (in my testing). Only backup lights improve light output from a functional perspective - I can see more backing up with LEDs than with stock bulbs.

I will update tonight - or as soon as I get more testing done. I want to figure out a process for turn signal LEDs, but only because it is a challenge.
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