LED tail lights weirdness

[Big Slim]

any one have success putting in LED bulbs in the tail lights? i put in the electronic relay made for LEDs so it wouldn't have the hyperflashing. Hoping with the electronic relay it would work just fine but not the case. the brake light worked fine with LED but the turn signals are weird. when say the left side is blinking the other side is blinking but lower brightness. which seems like it would have to be back feeding thru the brake wiring from the flasher wiring. i have the trailer wiring that has the led lights built in and when i unhook the ground to that the opposite side lights stop blinking but are a constant low light. putting the same lights bulbs in the front seem to work just fine.

 

[73azbronco]

Your LED setup, diodes and such, is backfeeding, ask manufacturer whats up

 

[Broncobowsher]

It will take some digital volt meter probing. I would be looking at the parking light circuit as well as the grounds. Don't rule out the fronts might be causing issues with the rears.
There isn't going to be a single quick it's always this answer for this. Methodical troubleshooting is the only way.

 

[Brush Hog]

Might be a polarity issue with the led flasher. Buy one of the things that reverses the polarity on the flasher. They are cheap. LEDs are finicky I had to flip bulbs,re
Do grounds and change flashers several times before they all worked.

 

[ntsqd]

My FSB came to me with LED tail lights in the OEM housings. Any time the ignition was on the tail lights glowed very dimly. The Cruise Control had never worked, but the PO claimed that it did. Out of curiosity I replaced the LED lights with regular incandescent bulbs. The glowing stopped and the CC started working. I talked to a MS-EE at my former employer about this and his take on it, and he is a car guy so he's not w/o some experience in things automotive, was that switches like the brake light switch work well enough for incandescent lights, but the turn-on voltage threshold for LEDs is so much lower that those switches "leak" enough voltage to cause the symptoms that I was having.

There are various ways to deal with this. Resistors in the wires, resistors that 'drain' the excess voltage to ground. I choose the easiest and left the incandescents in place.

 

[LUBr LuvR]

There’s two flashers behind the dash. Have you replaced both with LED flashers, or tried switching them? I had no turn signals when installing LEDs, but lights blinked when hazards were on. Needed the polarity reversers on one flasher, but not the other.

 

[Big Slim]

I have found i am getting 4v from both the cruise control and PCM on the brake line from the 5.0 motor.

 

[Big Slim]

i think a diode will solve the problem if i put one on these two lines. will keep them from back feeding voltage to the brakes and still get voltage when pedal is pushed. i tried the ford diode and some reason its not totally stopping the voltage. did reduce it to .7v. which does seem to make everything work properly.

 

[ntsqd]

https://www.amazon.com/dp/B01A77U122/?tag=classicbroncos-20

 

[Big Slim]

Actually a diode wont work. the cruise and maybe the pcm needs the ground thru the bulb as a reference.