Stumped, fender marker/turn light issue

[tadkingnkc]

Changed all bulbs on entire vehicle to LED. Everything worked perfect. All of a sudden, a month later the side marker/turn bulbs are burning faint rather than bright. Checked bulbs in another unrelated socket and they work fine. Thought it could be a ground issue but the front marker/turn bulb is burning bright so if it were a ground issue, I think they are on the same circuit so I’m confused. Both left and right side affected. Any suggestions?

 

[tadkingnkc]

Also should add that truck has LED flashers installed and I changed the turn signal indicators on the dash to LED peanut bulbs as well. Is this part of my issue?

 

[Snoots]

I believe side markers have a different ground location than the front bulbs. It does sound like a ground issue.

 

[SirRobyn0]

I'll tell you want we'd do at the shop. The very first thing we'd do is check the obvious, the grounds and power, if there is nothing obvious found, we'd pull all the LEDs out in that circuit and install the correct incandescent bulbs and see if it still does it. I know you said that you tested the LEDs, but I just don't trust aftermarket LEDs anymore as I've spent far to much time chasing problems caused by the the bulbs. IDK if this is really helpful or not, but basically I'm saying it might be worth while to pop an incandescent in just for testing purposes.

 

[tadkingnkc]

Grounds are good as ground is shared with front signal and it’s operating fine. So would changing to LEDs in the dash cluster indicator lamps in front of steering wheel, have affected circuit resistance? I’m thinking I should put an incandescent back in those to see if anything changes at the fender. Hopefully that makes sense.

 

[fast 99]

LED's sound like a good idea but they are more of a problem than a solution. An LED lamp is basically a computer circuit. They don't like poor connections or any resistance. These older vehicles were not designed to have a "clean" enough circuit. I have been able to dependably use them on clusters and side markers that have 194 bulbs, that's it.

Sockets for 1157 or 1156 bulbs won't provide a good enough contact. Some of you may disagree but that has been my experience.

 

[Turbo4whl]

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?

 

[SirRobyn0]

Grounds are good as ground is shared with front signal and it’s operating fine. So would changing to LEDs in the dash cluster indicator lamps in front of steering wheel, have affected circuit resistance? I’m thinking I should put an incandescent back in those to see if anything changes at the fender. Hopefully that makes sense.

Well I said one of the first steps at the shop diagnosing a problem like this would be to pull all the LEDs out and see if the problem persists. If you want to start with swapping the dash lights back to incandescent first that sounds fine to me, but be willing to swap them all back if need be. Read Wayne's post maybe be better to start with the fenders.

LED's sound like a good idea but they are more of a problem than a solution. An LED lamp is basically a computer circuit. They don't like poor connections or any resistance. These older vehicles were not designed to have a "clean" enough circuit. I have been able to dependably use them on clusters and side markers that have 194 bulbs, that's it.

Sockets for 1157 or 1156 bulbs won't provide a good enough contact. Some of you may disagree but that has been my experience.

Thank you. If I could like your post more than once I would. It seems like typically I'm the only guy saying stuff like "LED's sound like a good idea but they are more of a problem than a solution." I couldn't agree more.

 

[Dooley]

Most all the grounds in the "forward lamp harness" are in a press clip covered with duct tape inside the conduit approximately right behind/below the distributor. Pain to get at but often have found broken/cut wires here.

 

[WP29P4A]

We replaced the exterior bulbs on my son's truck and have had zero issues, makes me wonder if most of the issues you guys have seen are caused by people that only buy the cheapest product they can find. Seems like when I but the cheapest product, it always comes with side effects.

 

[fast 99]

We replaced the exterior bulbs on my son's truck and have had zero issues, makes me wonder if most of the issues you guys have seen are caused by people that only buy the cheapest product they can find. Seems like when I but the cheapest product, it always comes with side effects.

That could be possible. There is a difference in available quality. Where are you buying them?

A couple friends tried LED's although they were able to get them working why bother. Did buy some very expensive [for LED's] high output at $9 each for a dark Ford cluster. They worked fine.

LED's have a much lower amperage draw. If a circuit is overloaded due to added bulbs, I can see a reason for them. But for me the ones I have aren't dependable enough.

 

[scrap--metal]

LEDs in your dash are just fine. No need to change those out based on my experience. LEDs in the side markers is asking for trouble based on the circuit design.

@Turbo4whl explained it very well in my opinion. You shouldn't need an engineering degree to pick up what he's laying down.

Any questions?

How many years to obtain your wisdom?

 

[SirRobyn0]

We replaced the exterior bulbs on my son's truck and have had zero issues, makes me wonder if most of the issues you guys have seen are caused by people that only buy the cheapest product they can find. Seems like when I but the cheapest product, it always comes with side effects.

That could be possible. There is a difference in available quality. Where are you buying them?

A couple friends tried LED's although they were able to get them working why bother. Did buy some very expensive [for LED's] high output at $9 each for a dark Ford cluster. They worked fine.

LED's have a much lower amperage draw. If a circuit is overloaded due to added bulbs, I can see a reason for them. But for me the ones I have aren't dependable enough.

I will fully admit I know little about LED's. Yes I read Wayne's post and I've been told that before. I have basic understanding but have not gone out of my way to learn about them. I just know what I see and it doesn't seem like LED's in older vehicles work out for most people. Actually I cannot think of a classic / older vehicle that comes into the that has LED's that hasn't come in with a lighting complaint and the solution was removing some or all of the LEDs.

But Mike if they are working for you then enjoy them. Just remember this stuff for if you have a problem in the future so you know what to look for.

 

[82sbshortbed]

Had the same problem with these, so I just put back incandescent bulbs.

 

[tadkingnkc]

I understand all of this and am willing to concede that LED’s are the culprit. I just can’t figure out how the bulbs still test good at battery and they were working. Here is the photo with them working right after I put them in (and functioned just fine) and somehow now they burn dim. The only correlation to an “event” was when I changed all dash bulbs to LED as well.