3rd Brake Light Transmission Issue
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Cross-Country
Joined: Sep 2020
Posts: 77
Likes: 2
From: TX
3rd Brake Light Transmission Issue
I have read around a bit that having LED brake lights and also doing a 3rd brake light LED will mess with my transmission. Now I did the whole LED thing a while ago but just rebuilt my transmission so I dont want to ruin it again.
It is dang near impossible to find the lighting wiring for the incandescent bulbs, so I am wondering what if I just unplug it completely? What will that do to the PCM and torque converter?
It is dang near impossible to find the lighting wiring for the incandescent bulbs, so I am wondering what if I just unplug it completely? What will that do to the PCM and torque converter?
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Cross-Country
Joined: Sep 2020
Posts: 77
Likes: 2
From: TX
The LED were plug and play to the grey pin plug connector thing (sorry i dont know the proper terminology). But when i did my LED swap I tossed the old set up thinking I wouldn't need it. So now going back to incandescent I need the harness from the pin plug to the lights themselves.
More Turbo
Joined: Dec 2002
Posts: 664
Likes: 129
From: Columbia, MD
You might try adding more LED lights to create additional draw. I home-built a bed and put on LED tail lights, but I used 2, 4-1/2" round lights per side. Also added 3 LED tailgate bars daisy-chained into the flat-4 connector trailer connector. So more draw than LED bulbs in place of stock incandescents. Did not have transmission problems.
The flat-4 comes off the tail light circuit, so tailgate bars hooked into the flat-4 connector might be an easy way enough current draw to avoid problems.
The flat-4 comes off the tail light circuit, so tailgate bars hooked into the flat-4 connector might be an easy way enough current draw to avoid problems.
Butt-Head
Joined: Apr 2004
Posts: 9,470
Likes: 2,947
From: Reed Point, MT
The issues caused by LED lighting is not due to a low current draw.
The LED lights cause an issue because there is no path to ground through a physical filament when the brake lights are off.
There are resistors specifically designed for this issue but the selling point is usually to solve a fast-flash concern with the turn signals. Most people refuse to follow directions though and install them in series (because they've been told "current draw" on every automotive forum since 2002 even though a resistor in series actually reduces the draw) instead of parallel between the brake/turn wire and ground. This supplies a ground path to the PCM while the brake lights are off. Both sides must be done however as only doing one side, while functional while going straight, will cause issues when that side's turn signal is used (lost ground path).
The LED lights cause an issue because there is no path to ground through a physical filament when the brake lights are off.
There are resistors specifically designed for this issue but the selling point is usually to solve a fast-flash concern with the turn signals. Most people refuse to follow directions though and install them in series (because they've been told "current draw" on every automotive forum since 2002 even though a resistor in series actually reduces the draw) instead of parallel between the brake/turn wire and ground. This supplies a ground path to the PCM while the brake lights are off. Both sides must be done however as only doing one side, while functional while going straight, will cause issues when that side's turn signal is used (lost ground path).
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Cross-Country
Joined: Sep 2020
Posts: 77
Likes: 2
From: TX
Damn. where are you on every thread I read through. That makes alot of sense. I saw the resistor fix but thought it looked "really hacky". But since its not a current draw issue it makes so much more sense. I also have the fast flash issue but honestly I dont really care about that. I do care that I dropped money on a new transmission and dont want to spend that again for a long long time.
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Butt-Head
Joined: Apr 2004
Posts: 9,470
Likes: 2,947
From: Reed Point, MT
I have only posted this information on EVERY LED brake light thread and weird torque converter issue thread in the last 20 years.
Probably not EVERY..... but it seems like I am on the Broken Record Express.
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More Turbo
Joined: Dec 2002
Posts: 664
Likes: 129
From: Columbia, MD
Please keep repeating. Likely there are more folks like me who haven't read carefully enough to pick up the info. I definitely learned something today. For my setup, makes sense, I used LED trailer lights on my home-made bed. Left the stock incandescent bulbs in the 3rd brake light. I thought my lack of weird torque converter issues was because I used a LOT of LEDs in parallel. Now I know better. Thank you.
Thread Starter
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Cross-Country
Joined: Sep 2020
Posts: 77
Likes: 2
From: TX
Yeah I agree this was well needed. Learn something new everyday. TBH the LEDs for the third brake light are kind of ridiculous looking anyways. when I was 22 i thought they were the s*** but now I am wondering what in the world I was thinking.
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