Stumped, fender marker/turn light issue

[82sbshortbed]

Here's what mine did

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[Turbo4whl]

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


How many years to obtain your wisdom?

Too many. Started right out of High School in 1971 working on a utility fleet. Worked at a gas station while in H. S. Still wrenching now, a little slower....

 

[scrap--metal]

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.

The "event" was likely time and repeated use of the transistor(s) within each LED assembly. The side marker failure should be independent from your dash lights.

Like Wayne explained, below:

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...”

It's the transistor man!

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[tadkingnkc]

Ok so I put the 194 incandescents back into fender lights and zero light output at all. Front turn signals go bright when I pop it in and to dim when I remove them again. So faint light with Led and none with incandescent. Also, turn signal indicators in dash are solid on non blinking. Do I need to put traditional flashers back in in place of led flashers? Don’t pile on here. Genuinely even more stumped given everyone’s advice above to switch back to 194’s and my problem would be solved.

 

[tadkingnkc]

Also, I understood the lesson on transistors, but I don’t think my LED bulbs have them as they are polarity specific not universal polarity.

 

[Turbo4whl]

Ok so I put the 194 incandescents back into fender lights and zero light output at all. Front turn signals go bright when I pop it in and to dim when I remove them again. So faint light with Led and none with incandescent. Also, turn signal indicators in dash are solid on non blinking. Do I need to put traditional flashers back in in place of led flashers? Don’t pile on here. Genuinely even more stumped given everyone’s advice above to switch back to 194’s and my problem would be solved.

@SirRobyn0 advice is good. Replace all the bulbs with incandescents. Yes replace the flasher with original type and then test.

Do you have a bulb socket brush?

You must be registered for see images attach

Very handy tool for your old square truck. Make sure all the power is off when brushing. If this test does not fix the problem then you probably have a ground issue. Most models have the grounds bolted to the radiator support or fender. On a rare occasion the radiator support has lost it's ground to the rest of the body due to rust.

 

[WFO]

@SirRobyn0 advice is good. Replace all the bulbs with incandescents. Yes replace the flasher with original type and then test.

Do you have a bulb socket brush?

You must be registered for see images attach

Very handy tool for your old square truck. Make sure all the power is off when brushing. If this test does not fix the problem then you probably have a ground issue. Most models have the grounds bolted to the radiator support or fender. On a rare occasion the radiator support has lost it's ground to the rest of the body due to rust.

Other than the print, those look exactly the same as plumbing brushes for cleaning inside female copper fittings for solder.

 

[SirRobyn0]

Other than the print, those look exactly the same as plumbing brushes for cleaning inside female copper fittings for solder.

It's funny. Being an older mechanic I have a set of light socket brushes, but also being a farmer I have the occasion to need to do plumbing work. When I was first learning solder copper pipes I thought. I bet I could use my light socket brushes for that....

 

[tadkingnkc]

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?

Turbo4wheel, any thoughts now that I changed bulbs back to incandescent? Went from dim faint light with LED’s, popped em out and incandescent don’t light at all.

 

[scrap--metal]

Yes replace the flasher with original type and then test.

^ Has that been tried yet, in combination with the incandescent bulbs?

 

[tadkingnkc]

Yes. Original flasher and incandescents. Turn signal indicators on dash and out front on bright constant with no blink and fender lights nothing.

 

[scrap--metal]

I don’t think my LED bulbs have them as they are polarity specific not universal polarity.

If the LEDs you have are polarity specific, I'm confused how they worked correctly after the initial installation. I believe you when you say they did work, but it goes against what Wayne explained in the turn signal circuit (post #7). It seems as though they should never have worked (i.e. flashed) because of the circuit design.

Yes. Original flasher and incandescents.

Did you swap the flasher for your hazard lights in addition to the turn signal flasher? Either swap it initially with the LEDs, or swap it back during the trouble shooting? I'm pretty sure they're two separate flashers.

 

[AuroraGirl]

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.

This. an LED bulb with exposed chips which are found for cheap work OKAY in interior lights, if they dont ghost light up, but on outside lamps it doesnt take long sincve they arent perfectly sealed. Especially with a foam gasket thats 40 years old

 

[Turbo4whl]

Turbo4wheel, any thoughts now that I changed bulbs back to incandescent? Went from dim faint light with LED’s, popped em out and incandescent don’t light at all.

Okay, do the front parking lights and turn signals work okay now and just the fender markers are out?

Were you able to clean the 1157 bulb sockets? Remember the fender markers need the front park/turn lamps to work correctly.

You can also clean the contacts in the fender sockets. The best way I have found to clean them is to take a piece of 220 wet or dry sand paper. Tear a 1 inch piece off the sheet and then fold it back on it's self 2 times and make a small sanding stick. You can also do it with a thin finger nail file after trimming it to fit in the socket. With the finger nail file, it must be thin, you don't want to bend the socket contacts. It is hard to bend the contacts with the sand paper. Safer method.

 

[tadkingnkc]

Well, I can’t explain it but changed the front to incandescents but tried the LED flasher with incandescents and boom. Everything works! Perhaps the leds in the turn indicators on the dash are requiring the use of the led flasher even though I’m back to incandescents outside of the cab. Thanks to everyone.