Switching to LED external lights and ran into this...

[Knuckle Dragger]

Somebody call Scooby-Do to solve this ***** because it's kicking my arse. I tried all kinds of stuff and I ended up pulling out the relays for the LEDs turn indicators and got back to just them glowing a little with the lights on. I found if I pull the corner lights out completely the turns all work without a glow. I tried the incandescent bulbs and three different LEDs with the exact same result.

Anyone run into this?

EDIT: Fred and the gang came by to find the demon haunting my truck. Thelma found if we run one incandescent 1157 bulb on each side the issue clears up. My guess is if I run the resisters one one bulb each side it's going to work. Anyone have a suggestion for a resister kit?

 

[delta_p]

One thing to keep in mind with the led's, or any diodes for that matter, is their forward voltage. This the minimum voltage needed in the forward direction to allow current flow.

In the exterior front light circuits the marker lamps find ground through the many bulbs on the splice. In normal operation the voltage drop across the marker will be high enough that the lower voltage on the bulb path to ground won't glow the bulbs.

If you put led's in, and the marker lamp drop doesn't provide enough voltage to produce the forward voltage through the led, then the current will look for the next easier path...an indicator lamp maybe.

The led may have a forward voltage of ~1.9 - 3 volts to allow forward current. A 191 bulb will glow at that.


An 1157 is 26.8W @ 12.8 volts (2.1 amps), on the high element for the turns. At 8.3W @ 14 volts for the constant low current parks (.6 amps). The equivalent resistance of the high element is ~6ohms.

Since the marker needs a ground path with the parks and the flasher alternates off, so the marker can alternate flash with the turn lamps, I put a ~6ohm resistor across the turn lamps and made sure it was at least 50 watts rated. This way it won't get too hot since when voltage is applied during a turning timeline in traffic.

 

[Knuckle Dragger]

One thing to keep in mind with the led's, or any diodes for that matter, is their forward voltage. This the minimum voltage needed in the forward direction to allow current flow.

In the exterior front light circuits the marker lamps find ground through the many bulbs on the splice. In normal operation the voltage drop across the marker will be high enough that the lower voltage on the bulb path to ground won't glow the bulbs.

If you put led's in, and the marker lamp drop doesn't provide enough voltage to produce the forward voltage through the led, then the current will look for the next easier path...an indicator lamp maybe.

The led may have a forward voltage of ~1.9 - 3 volts to allow forward current. A 191 bulb will glow at that.


An 1157 is 26.8W @ 12.8 volts (2.1 amps), on the high element for the turns. At 8.3W @ 14 volts for the constant low current parks (.6 amps). The equivalent resistance of the high element is ~6ohms.

Since the marker needs a ground path with the parks and the flasher alternates off, so the marker can alternate flash with the turn lamps, I put a ~6ohm resistor across the turn lamps and made sure it was at least 50 watts rated. This way it won't get too hot since when voltage is applied during a turning timeline in traffic.

Awesome, parts ordered. Thank you for the great explanation

 

[Knuckle Dragger]

I put a ~6ohm resistor across the turn lamps and made sure it was at least 50 watts rated. This way it won't get too hot since when voltage is applied during a turning timeline in traffic.

This fixed my turn signal issue and the hazard issue. Everything works as it should now.

I broke the high beam indicator as I was adjusting it so it will be a few weeks before it's all back together. I'm literally waiting on a slow boat from China for the replacement. I don't understand why no one sells icon specific LEDs for the indicators here in the states.

 

[sewlow]

I see no mention of you swapping the flasher unit for an EP-29. They're digital-based as opposed to load-based.
I HATE load resistors. F'n fire hazards.

 

[delta_p]

will a EP-29 fix the indicator glow? he needs a ground path for the marker too. I had to put load resistors in for that, and then also a EP-29 to prevent the hyperflash from the low current. I also put in switch back so had to resistor each one anyway to allow the switching circuit to work.

They do get hot though, especially if you put them anywhere but across the turn lamps.

 

[sewlow]

My '97's all led except for the middle tail light bulbs. Putting an LED in that spot blows fuses as soon as the lights are turned on.
EP-29 is the only other change I made. No glow from any of the dash lights/signal indicators. Everything works as it should.
There are LEDs that have the prefix 'C/K' which work the best in these trucks & will also allow the dash lights to be dimmable, unlike the reg. LEDs.

 

[Knuckle Dragger]

I see no mention of you swapping the flasher unit for an EP-29. They're digital-based as opposed to load-based.
I HATE load resistors. F'n fire hazards.

I cut a leg off the factory flashers processing chip as I saw in a post by someotherguy https://www.gmt400.com/threads/how-to-stop-led-fast-flash-info.5208/page-2 (about half way down the page) to stop the hyper-flash. I put the resisters in a well ventilated spot away from everything. I let the signal run 10 minutes and they weren't cold but not hot enough to worry me. My seat heater gets warmer and my arse and seat are still intact As you say, they DO get warm and that should be a consideration for where you secure them.

My instrument cluster is custom and the turn indicators are LEDs. I'm not sure if you would have still had the glow across a incandescent 194.

 

[Knuckle Dragger]

My '97's all led except for the middle tail light bulbs. Putting an LED in that spot blows fuses as soon as the lights are turned on.

That takes a different bulb, again posted by someotherguy How to stop LED Fast Flash info

Explained well here: http://store.ijdmtoy.com/LED-Turn-Signal-Reverse-Backup-Tail-Light-Bulbs-FAQ-a/487.htm

 

[BDBerry]

Gents, I replaced all my exterior lighting on my 99 K1500 Suburban with LED except for the 3rd brake light. Initially I had problems with my flashers and hazards until I replaced my flasher control relay under the dash with a digital one I found on EBAY. Fixed all my problems. Hope this helps.