Led conversion (running/turn signals)

[squarebodysteve86]

Hi all, new here, hopefully I'm doing this whole forum thing right. They've always helped me in the past, even when the threads are 10+ years old. Idk where else to ask or who to turn to for advice here so, desperate attempt here. I'm converting all of my lights on my 86 c20 to led. Just doing bulbs, not the overpriced lmc led panels. Headlights have been led for a while so this is all going to be pertaining to the turn signals and running lights. I'll do my best to explain, so bear with me. Using an led flasher relay (I've tried several). Front leds are Switchback (running lights white, turn signal yellow). Issue I'm having is the leds are feeding back into the turn signal circuit. I've swapped the led to incandescent and I have very small voltage to the blue wire with running lights on. Leds feed back around 11.5v, enough to be a problem. I've tried other leds. Reading an old forum somebody mentioned diodes. So I read up and got me a pack of many different ones. Including 1n4001 and 1n4004. What I'm trying to figure out is how do I wire this up to keep my front leds from backfeeding into the turn signal? It's also causing an issue where the 194 fender led will not work. I appreciate feedback and apologize for the run on, I just try to be as in depth as I can.

 

[Dleslie212]

I'm getting ready to do this myself. What do you mean by it back feeling?

 

[Scott91370]

What are you using to power the white light?
Do you have a GOOD ground? This is usually the problem with electrical.

Please post up a picture of the wiring on the lights so we can get a visual reference as well.

 

[fast 99]

FYI, LEDs are a computer circuit. These trucks were not designed for a circuit with a clean enough connection. Many people have tried them [including me] without success. The slightest resistance they won't work.

 

[squarebodysteve86]

I'm getting ready to do this myself. What do you mean by it back feeling?

When the running lights are on (brown wire) and led in the socket, it sends voltage back to the turn signal circuit (blue wire) only does it with and led bulb

 

[squarebodysteve86]

FYI, LEDs are a computer circuit. These trucks were not designed for a circuit with a clean enough connection. Many people have tried them [including me] without success. The slightest resistance they won't work.

I've converted other older vehicles to led with hardly any issue I couldn't figure out myself. I'd reference my k30 if it wasn't torn down for work right now

 

[squarebodysteve86]

What are you using to power the white light?
Do you have a GOOD ground? This is usually the problem with electrical.

Please post up a picture of the wiring on the lights so we can get a visual reference as well.

I'm at work so this is as good as I can get for now. Grounds are good. Bare metal, clean, I went the extra mile to clean up all my grounds because I know how picky they are.

 

[Scott91370]

I highlighted a part in your pic, does the blue wire connect to the brown here?

You must be registered for see images attach

 

[squarebodysteve86]

I highlighted a part in your pic, does the blue wire connect to the brown here?

You must be registered for see images attach

No sir, just the way I drew it, added the 194 just as reference at the end.

 

[VintageAF]

It's also causing an issue where the 194 fender led will not work.

When you say the fender lights do not work, does that mean they won't illuminate as a park light should or they don't flash when being used as a turn signal?

 

[Edward Koleman]

Are you running the led flasher relay with the external ground wire? It will make a difference. I've converted my 87 to all led bulb with original sockets and have not had any problems. If you are running that style relay, it's probably going to be the switchback bulbs giving you the issue.

 

[WP29P4A]

There is a problem with your diagram, it shows 2 Positive feeds to the 194 bulb, and no negative connection. I learned from doing the LED conversion on my son's truck and a 2006 Jeep, Incandescent bulbs don't care about polarity, LED's will NOT work correctly if the polarity is not 100% correct.

I had to verify pin placement on every plug connected to the head lights and running/turn signal lights to correct the issues. The first clue for me was the headlights worked perfect before I changed to LED. Then the 2 LED headlights would act differently when I turned the headlights on or switched to high beam. Once I corrected the pin configuration, everything worked.

The place where the DIY crowd gets stuck is the logic that, the incandescent bulbs work but the LED bulbs don't. Causes them to focus on the wrong area. You can not compare the two technologies. One is a controlled short that produces heat and light, the other has a control circuit connected to the bulb. Kind of like comparing the electrical system in a 74 Chevy truck to a new Chevy truck.

 

[Turbo4whl]

@squarebodysteve86

1. Easy fix, disconnect the shared lead from each respective fender marker light and it's turn signal feed wire. Add a ground to that wire on the 194 bulb. Seal off the wire to the 1157 turn bulb.

Yes, now the side marker will only work when the parking lights are on, they will not flash with the turn signals. No more feedback problems.

There is a problem with your diagram, it shows 2 Positive feeds to the 194 bulb, and no negative connection.

The diagram for this sentence is correct. No the blue wire is not connected to the brown wire. The 194 has two positive feeds, read on.

This posted before to explain it all:

2. Why LED’s may not work well in GM fender marker lights:


First you need to understand that the fender 194 bulbs do not have a dedicated ground. One contact is wired to the positive parking light wire, the other contact to the respective turn signal wire, (right or left).


This is how they work without a dedicated ground: If the turn signal is off and the parking lights are on, current from the parking light wire through the 194 bulb then follows the other wire to the turn 1157 bulb. Current moves through the turn filament of the bulb to ground. The 1157 bulb does not light because the filament requires more current than the 194 bulb lets through. The same is true if the parking lights are off and the turn signal is on, the parking light filament becomes the ground. So if the parking lights are on, then you turn on the signal, the 194 bulb blinks off, and both contacts of the 194 bulb have current and no ground.


So of course the side marker will never work if the 1157 bulb is removed or burnt out or have a bad ground. Keep in mind at this time current can be moving in either direction in the 194 marker bulb.


Electricity 101: What is an LED? = Light Emitting Diode. What is a diode? Many kinds of diodes but we’ll keep it simple. A diode is a check valve, only lets current flow in one direction. So how can a 194 replacement LED bulb even work? Current needs to flow both ways? The bulb has a transistor!


What is a transistor? The simple definition is it is an electronic switch. The switching transistor has four connections, two from the bulb socket contacts, the other two connections to the LED. The transistor senses which way the current is flowing and directs it to the proper connections of the LED. This transistor in the 194 LED replacement bulb is very small. The transistor originally thought to be needed only a few times, depending which way the non polarized 194 bulb was installed.


So when used in a GM fender application that transistor is switching all the time. The transistor only signed up to switch a few times. Now it is switching way more and it says, “I didn’t sign up for this, I’m out of here...”

Any questions?

 

[squarebodysteve86]

When you say the fender lights do not work, does that mean they won't illuminate as a park light should or they don't flash when being used as a turn signal?

They won't work at all. As I said, the 1157 running light circuit is sending voltage back into the turn signal circuit. So I'm trying to use diodes to keep the power directional.

 

[squarebodysteve86]

@squarebodysteve86

1. Easy fix, disconnect the shared lead from each respective fender marker light and it's turn signal feed wire. Add a ground to that wire on the 194 bulb. Seal off the wire to the 1157 turn bulb.

Yes, now the side marker will only work when the parking lights are on, they will not flash with the turn signals. No more feedback problems.


The diagram for this sentence is correct. No the blue wire is not connected to the brown wire. The 194 has two positive feeds, read on.

This posted before to explain it all:

2. Why LED’s may not work well in GM fender marker lights:


First you need to understand that the fender 194 bulbs do not have a dedicated ground. One contact is wired to the positive parking light wire, the other contact to the respective turn signal wire, (right or left).


This is how they work without a dedicated ground: If the turn signal is off and the parking lights are on, current from the parking light wire through the 194 bulb then follows the other wire to the turn 1157 bulb. Current moves through the turn filament of the bulb to ground. The 1157 bulb does not light because the filament requires more current than the 194 bulb lets through. The same is true if the parking lights are off and the turn signal is on, the parking light filament becomes the ground. So if the parking lights are on, then you turn on the signal, the 194 bulb blinks off, and both contacts of the 194 bulb have current and no ground.


So of course the side marker will never work if the 1157 bulb is removed or burnt out or have a bad ground. Keep in mind at this time current can be moving in either direction in the 194 marker bulb.


Electricity 101: What is an LED? = Light Emitting Diode. What is a diode? Many kinds of diodes but we’ll keep it simple. A diode is a check valve, only lets current flow in one direction. So how can a 194 replacement LED bulb even work? Current needs to flow both ways? The bulb has a transistor!


What is a transistor? The simple definition is it is an electronic switch. The switching transistor has four connections, two from the bulb socket contacts, the other two connections to the LED. The transistor senses which way the current is flowing and directs it to the proper connections of the LED. This transistor in the 194 LED replacement bulb is very small. The transistor originally thought to be needed only a few times, depending which way the non polarized 194 bulb was installed.


So when used in a GM fender application that transistor is switching all the time. The transistor only signed up to switch a few times. Now it is switching way more and it says, “I didn’t sign up for this, I’m out of here...”

Any questions?

I do appreciate the in depth response but wiring is not my strong suit by any means. So, honestly, it's kind of hard for me to understand. The thing I have a hard time understanding is, I have a video of this exact truck with all these leds working, running lights and turn signals, as it was supposed to. And now for whatever reason, they do not. I know they can work. I've seen it.