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Discussion Starter · #1 ·
I bought some new LED lights and a flasher relay and installed them and noticed a strange issue. When the headlights are off, everything works ok, but when I turn the headlights ON, I am greeted with some dash warning lights (in photo) as soon as I use my turn signals, and the tail lights both blink along with the turn signal. Either right or left. This only seems to be happening when my headlights are on though.
I did try going back to the original bulbs (eliminating my new stuff from the equation) and the same issue was present. This issue was not present until I attempted to replace some bulbs. I have read a few posts saying that it could be the brake switch, but so far the brake lights seem to be working as expected. I do not see any frayed or chewed wires, so I don't know if I can point a finger at the squirrels yet either. I do not notice anything else with any other lights. I did check in the fuse box (inside and under hood) and I could not find any blown fuses.

Speedometer Odometer Trip computer Light Gauge


Is this something that any of y'all have seen? I'm located in Sacramento, CA too if anyone has any suggestions for a shop that's good with FJ electrical, should it come to that.

Thanks!
 

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Maybe it is the flasher relay but it appears you removed it as well correct?

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Discussion Starter · #5 ·
Maybe it is the flasher relay but it appears you removed it as well correct?

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Indeed I did. Went back to the original bulbs and the flasher relay (which was a pain to get to on the back of the fuse panel) and the problem persists.

I'll drop by a nearby auto parts store and see if it's throwing a code.
 

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Pull the fuse for the headlights and then try and turn them on and test and see what happens... You mentioned the flasher relay was in a tight spot, maybe you disturbed something. Take some pics with your camera and zoom in, it may show something.

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Discussion Starter · #7 · (Edited)
Pull the fuse for the headlights and then try and turn them on and test and see what happens... You mentioned the flasher relay was in a tight spot, maybe you disturbed something. Take some pics with your camera and zoom in, it may show something.

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I tried this. Only thing that happened was no headlights. I did pick up a couple spare fuses and a fuse tester today, though.

edit: I just remembered... I replaced both mirror lights, and both license plate lights as well. facepalm I did not put those back to factory yet because one of the old bulbs was dead.
 

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Did you replace those with LED versions?
 

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Discussion Starter · #9 ·
Did you replace those with LED versions?
the mirror lights and license plate lights? Yes, I did. I completely forgot to put those back to stock.

I'm about to walk over to Auto Zone and pick up a bag o' bulbs and get everything back to stock.
 

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I tried this. Only thing that happened was no headlights. I did pick up a couple spare fuses and a fuse tester today, though.

edit: I just remembered... I replaced both mirror lights, and both license plate lights as well. facepalm I did not put those back to factory yet because one of the old bulbs was dead.
Sorry... When you pulled the fuse for the headlights the dash light alarms went away or were they still there when you turned the headlights on? Just trying to connect the dots...

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Discussion Starter · #11 ·
Sorry... When you pulled the fuse for the headlights the dash light alarms went away or were they still there when you turned the headlights on? Just trying to connect the dots...

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ah! at that point, I had no lights. No headlights, no working lights. I'm about to make an update, it got even stranger. lol.
 

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Discussion Starter · #12 ·
1800 Update:

Went to the store and got some stock tail light bulbs and turn signal bulbs. I did not touch any of the other bulbs.

Put new cheap $4 Sylvania bulbs in both turn signal and tail lights. put the stock flasher relay back in place. everything worked.

Put the CF-18 smart tap flasher relay on with"normal" bulbs. Everything worked.

put the LED turn signals in. everything worked. (head scratching occurred too.)

Hmm. Then I tried both of the red LED tail light units on the right side (leaving a Sylvania bulb on the opposite side) and everything worked.

tried both of the red LED tail light units on the left side, and they both worked. so I have established that each bulb does work by itself.

scratched my head again, and removed the Sylvania cheapie bulb and put the red LED tail light units back in.. one on each side, and my problem came back. Dashboard lights came on, just like before.

it seems like the problem only happens when I have BOTH of the red LED tail light units in place. The LED turn signals are working as expected.

Right now I have Sylvania bulbs for tail lights, diode dynamic LED turn signals, and the CF-18 SmartTap flasher relay, and everything is working as expected. Oh, and LED license plate bulbs, LED mirror light bulbs, and I think Sylvania headlamp bulbs. I never touched anything up front, it's all standard stuff. I was only working on the back.
 

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This is good to know. There must be some sort of weird current flow in the system with LED's in the taillight position messing with the CAN, so no replacing the taillights with LED's I guess.
 

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I have led brake lamps, they flash three times before going steady on. That is by lamp design but point being maybe pick up one or two different brake lamps and try them.


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Discussion Starter · #15 ·
This is good to know. There must be some sort of weird current flow in the system with LED's in the taillight position messing with the CAN, so no replacing the taillights with LED's I guess.
I did reach out to the vendor again with the updated troubleshooting information, and they had already sent out a new set of bulbs for me to try out and see if it still happens.

post office has been pretty slow but when they get here, I'll give them a try and see what happens. this may have been as simple as "oops, J got a defective part." It's been kind of fun trying to figure out, though. Helps fill up some of my abundant free time. :D
 
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