LED Turn Signals Cause Dash Turn Signals to Glow With Headlights On

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GoreMaker

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Yesterday I did a front grill swap on my 1999 Suburban K1500, and while I was at it I replaced all the turn signal bulbs with LEDs. I'm using an electronic flasher relay from LMC Truck. I did all 4 front bulbs (1157) and both corners (194), all in amber.

Now, when my headlight switch is set to turn on the parking lights or headlights (so any position other than "off"), both turn signal lights in my instrument cluster are glowing dimly. Everything appears to be functioning as expected, the turn signals flash and the 1157s and 194s alternate, the flashing is a very regular interval, and my turn signal lights in the dash blink as expected. The dash turn signal lights even turn all the way off while they're blinking. The corner lights (194) are also dimly on all the time along with the dash turn signal lights. And they blink all the way on and off with the turn signals.

I'm not sure if maybe I have one or both 194s in backwards (do they have a direction when they're LEDs?), or if this is just a side effect of running all front LED lights. Technically the functionality is fine and it causes no driving safety issues, it's just kinda distracting from the driver's seat. Before I start taking things apart to try flipping the 194 bulbs around, I figured I'd ask in case someone else knows what might be causing this.
 

GoreMaker

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Figured it out. I had purchased CAN-bus compliant 194 bulbs, but they didn't seem to behave properly. I switched to some non-CAN-bus compliant LED bulbs that I had laying around and now everything works as expected. No more dimly lit turn signal indicators or dimly-lit 194 corner bulbs. The corner lights are on at full brightness when they're supposed to be. Also, the 194 bulbs I bought originally had 5 LED chips on them and were a bit long for the light housing, I struggled to twist them in and they were pressed up against the lens. The other 194 bulbs I had on hand only have 2 LED chips and are housed in a glass enclosure, like traditional ones. They're exactly the same size as traditional 194 bulbs. They fit perfectly, and they're just as bright as the 5-chip ones.
 

HotWheelsBurban

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Figured it out. I had purchased CAN-bus compliant 194 bulbs, but they didn't seem to behave properly. I switched to some non-CAN-bus compliant LED bulbs that I had laying around and now everything works as expected. No more dimly lit turn signal indicators or dimly-lit 194 corner bulbs. The corner lights are on at full brightness when they're supposed to be. Also, the 194 bulbs I bought originally had 5 LED chips on them and were a bit long for the light housing, I struggled to twist them in and they were pressed up against the lens. The other 194 bulbs I had on hand only have 2 LED chips and are housed in a glass enclosure, like traditional ones. They're exactly the same size as traditional 194 bulbs. They fit perfectly, and they're just as bright as the 5-chip ones.
Good to know, where did you source these LED bulbs? That sounds like what I would like for my trucks. 4 high and upper corner lights are in the plans....so many places to spend money and so few places to get money!
 

GoreMaker

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I recently got done the 4-high relay, heavy duty headlight relay, all LEDs everywhere (except headlight bulbs), and replaced the cracked front grille. The headlight output is dramatically better, even just the low beams. The LED blinkers, running lights, brake lights, reverse lights and plate lights are wonderful. And the electronic blinker relay from LMC Truck is better than I could've hoped. It actually clicks! None of the electronic relays I've used before ever clicked audibly. I got all the LED bulbs from superbrightleds.com

Here's what I ordered that worked:

2x of these (194 amber) for front corner lights
2x of these (194 cool white) for license plate lights
4x of these (1157 amber) for front turn signals
2x of these (3156 warm white) for reverse lights
4x of these (3157 red) for rear running/brake/blinker lights

Technically the top bulbs in the taillights could be 3156 red since they're just a single mode bulb that never blinks or brightens, but I wanted to make sure the top and middle bulbs were the same brightness when the running lights are on, so I got identical 3157 for all 4 of those. Worked out perfectly. The second (brighter) mode of the top 3157 just never gets used.

By the way, the 4-high relay kit that LMC Truck sells includes #@%$*& Scotch Lock-style wire taps. Those damn things should be illegal, I can't believe anyone is still using those in this day and age. Do yourself a favor and get some Posi Taps for 18ga wire. Those are infinitely more reliable, and you won't end up with wires that look like this (electrical work done by previous owner):

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SentandBent4x4

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I recently replaced my my grille with a satin black one, and threw on some smoked lamps and LED headlights. I order the four beam high wiring kit, but it hasn’t arrived yet. I put amber LED blinkers in as well. I didn’t need a relay, because it was plug and play. Worked great for a few months, but now all of a sudden when I turn my headlights on, the right blinker light comes on, and it wont blink. The blinker it’s self doesn’t turn on, the icon just glows. The left one doesn’t do that, and it works as should with the headlights on. I’m stumped as to what the problem is. I might also mention that the AC display went almost completely out, only one icon shows on it, and it’s unresponsive. I don’t know if the problems are related, or separate. I live on a farm, so I was wondering is mice chewed it?
 

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