Sequential LED strip not working when car is turned on.

The wiring.

The power line in the headlight, side marker or fog light harness will be at a lower voltage (e.g. 12 V or lower depending upon the current load) than what is available at the fuse box. Run a wire from the headlight fuse directly to the Input of the voltage regulator and run the return back to the battery negative terminal.

Then run the Output of the VR to the input and return of the LED box. Any current out of the VR Output (+) must be returned back to the “ground” or return (-) on the VR Output side. Not to the chassis. Chassis is used to carry current back to the battery negative terminal which originated from the battery positive terminal. The VR Output is created by a transformer and is a separate power supply from the battery.

If the voltage to the VR input drops to 12V or less, then it no longer can sustain its Output. This will cause a power glitch or reset to occur in the LED box and cause the goofiness that you are seeing.

Thanks for the reply.

All the lighting and a few other things (locks/windows) are controlled by a footwell lighting module. I have a fuse box and relays but nothing is listed for lights, just the light module.

I wish I got into any car related circuits years ago. I see videos of people creating nice lighting set ups, especially sequential led strips in the tail lights and I envy them.
I work on this light project for about an hour a day. Either when I think of something else to try or have directions from you all here on what to do.
Currently I just have the wires twisted together. I hard wired everything like 3x only to find out it was incorrect. I will hardwire everything once it’s 100%.

Thank you for the reply.
It makes sense what you’re saying about the grounds.
The thing is, I’ve looked at my fuse box diagram and I don’t have any headlight fuses.
Just fuses for the lighting module.
But, I can adjust the voltage sent to lights.
What if I tell the lighting module to send 14v to the fog lights? Or is 14.5 better?

I could then wire the VR input wire to the foglight power wire which would be receiving more voltage.
Or will the load of the existing foglight bulb draw too much power away? It’s a led bulb in the foglight.
Another option (if the above works and as a last resort) would be to send 14v to the factory turn signal bulb on the headlight but remove the bulb so there is no load?

The battery is located in the trunk. There are some ground points in the engine bay.
Would it be ok to ground the VR input on these?

For the VR output, you’re saying to wire it the following way, correct?
VR +output to led box power wire
VR -output to led box ground wire
Then led box signal wire just stays on the side marker.

Thanks to both of you.

it looks like you have BMW E90, do you get light bulb burn-out error on the dash? on ignition the LCM check every bulbs, the computers might think you have a bulb out condition and shut off the signal to the bulb usually after few seconds of ignition. The same things happened when you replace headlight with LED or HID it will switch off the corresponding light if the LCM thinks that the bulb is out. There are LED bulbs with proper wiring or load to simulate filament bulb to overcome this issues (the so called CANBUS safe)

You probably get better answer in e90 forums.

Yes, I do have the e90.
No, I do not get light bulb error warnings. All the light bulbs are still in place, I was just tapping into them.
I have asked there already and no one knew what I was talking about.

Ok I tried it out again.

The wire I am pulling power from on the headlight reads 14.5-75 volts.
I connected to VR input wire to it and grounded the VR input wire on the chassis.(chassis measured 14.5-75v when I tested the headlight power wire)

I measured power coming out of the VR output wires. It measured 12.29v.
I wired the VR output power/ground to my power/ground on the led box.
At this point, the led box is only wired to to the VR and signal wire to the side marker signal.

It worked the best wired this way, still a small stutter. Not a full reset of the led, but there are times when the sequential part of the led strip is flashing and it will flash quick once or twice and then flash in a smooth motion.
The strip says 12v 3A operating voltage. The VR says output 12v +/- 2%. Would .29v cause issues?

I ordered a second VR. Listed as output 12v 5A. I wired it up, output voltage was 12.32.
This time, the led strip would do the sequential flash 3-4 times and do a full reset.
IE: turn off completely, revert to daytime running light, and then start flashing.

NOW the first VR (12v3A) is doing the same thing! Flash, turn off, restart, flash repeat.

Is that with the circuit fully loaded (with the headlights ON), or Open Circuit Voltage?

Find the fuse that feeds the headlights, or the power module device, and connect at that point as your source.

Put a voltmeter on the Output of the VR and monitor what happens when the blinker is working—does the voltage hold rock hard solid at 12V, or does it lay down and limp out?

Thanks again.

I will try connecting to the fuse tomorrow and see what happens.
When I checked for voltage at the VR earlier, I remember it being steady. But I wasn’t paying attention, so it may have jumped around if I left the meter on it longer.
I did check voltage at the signal wire coming from the side marker. I read that one jumping from like 2v to 10v. I figured this is because the car sends signal flashes to it….?

I put together a video showing the led strip functioning a few different ways.
I added text to the video but I’ll explain it again here.

*First clip*shows the strip wired to a battery from an impact gun. Unsure of the voltage on that, I can check tomorrow. But it seemed to have a steady flash.

Second clip shows the strip flashing pretty smooth with a quick flash or 2 once in a while. You really need to pay attention to the strip to notice it.

Third clip shows the strips having a lot of hiccups with slowing down and speeding up.

Fourth clip shows the strip completely restarting every 2 flashes.

The wiring from clip 2-4 was all the same.
Input VR from the car, output to the led box and led box signal to side marker.

Silly question, maybe, but you sure the ones you got ain’t defective?

Imagine if they all did the same thing, other people might piss’n’moan about it in the reviews, no?

If you are going to troubleshoot electrical issues then using the voltmeter is your only hope.

Clip 1 proves that the LED box will work correctly with a good clean power supply at yy Volts.

Clips 2-4 prove that it will not work using the VR Input at nn Volts, and the Output at xx Volts.

Until you have some voltage measurements you really have no way to identify the issue.

The VR may be defective, or inadequate for the task, or not supplied adequately for the task—but you have no data to prove any of these 3 conditions.

We can only guess about what is happening based upon what you tell us.

My guess is that the Input voltage to the VR is fluctuating or hits a voltage below the rated input range, and the Output is causing the LED box to reset and hiccup. My guess is that the headlight harness is regulated and controlled by a module that may measure and limit current such that adding a 36 Watt load to one of the legs causes an issue. There may be relays or transistors with PWM supplying the harness, but it doesn’t like the extra load.

But this assumes that the VR is not defective and can function as advertised, and this has not been tested or verified to be true, so the VR would need to be tested separately to prove it is up to the task.

Assuming the VR is okay and up to the task, the best power source for it is from a fuse circuit directly in the fuse box.

Modern cars run more than just current thru wires, today all car’s functions controlled by modules, there are very few power wires that do not carry signals now. if you want to add an accessory to a car, you are better off knowing what each wire carries, or bypass factory wires all together for power,

I’m at a loss, too, but I suspect you need to dive deeper into the FRM settings that you are apparently altering with that firmware/software app. And I guess be positive that the FRM is known good? Reading a bit about those and allll of the issues and recall, that one piece seems like a royal pita to both understand and diagnose even with the scanner info.

This is a lot more complex than what many cars use, certainly more than the ol’ basic relays and such, plus you have an awful lot going on with add-ons and alterations of voltage to various circuits, etc. Do you suppose the people that created that app could provide some detailed assistance? I would imagine that most mechanics would be clueless and BMW dealer shops would shoo you away instantly.

I think I got! but I’ve said that so many times that I could be wrong.

I placed an order for a new set, I just need to return this one within a certain time frame.
Luckily it’s not installed 100% yet.

I had previously measured voltage and it was in fact dropping down. I’m guessing it was working.
These are some measurements I got today when I pulled power from the footwell module in the fuse box.
Input voltage at VR 14.77-14.83
Output VR voltage going to LED box 12.28-12.31.
I measured the voltage on the impact gun battery. 17v.
I thought it was odd how the strip worked fine when wired to the impact battery, at 17v…

I tried to find a wiring diagram, but only found one for the same car as mine but different headlights, it helped a little. At the very least, I needed a factory wire for signal for the sequential flasher.

There are some issues with the FRM modules. Usually all lights stop working or windows stop working. Mine has no fault codes.
Great idea for contacting the makers of the app, I did. They said something about Pulse width modulation and to mess around with voltages. They weren’t familiar with trying to add any aftermarket lighting.

Today’s results.
After pulling straight power from the fuse box, I wired the led signal wire to the side marker and it worked!…For 5 minutes.
I re started the car and now I have the same issues.

I adjusted the foglight voltage to receive 12v, so I wired the led box to the foglight, same deal.

Back to above. Why does the strip work with 17v from the battery pack?
Why does the day time light on the led strip work fine on any power source and the flasher has issues?

I pulled the signal wire off the side marker and touched it to a power wire for the corner light/turn signal on the headlight and it flashed normally.
That wire reads anywhere from 1v-10v when the turn signal is on.
Earlier I mentioned the side marker light was measuring 10v. I was wrong, it measured
1v-4.5v, today.

It appears the power/ground wires were fine, it was the signal wire that wasn’t receiving enough voltage. The low voltage for the signal wire was making the strip revert to the daytime running light, I assume.
When the signal is wired to the corner light(also a turn signal) on the headlight harness, it works fine when flashing.
I thought the signal wire was just that. Thought it sent a signal to the led box that said “ok flash”. I didn’t think the signal also needed voltage, and if someone mentioned it, I completely missed it.

The downside, I had the corner amber light set to be on 24/7. I had to disable it, because if its on, the sequential flasher is constantly on.
Unless I can increase the voltage on the side marker, I think this is how it will have to stay.

I also couldn’t get the led strip and corner amber light to sync up.
They flash together for a bit and then go out of sync, if that makes sense.
I just disconnected the corner amber light. It won’t ever turn on now, unless I can increase voltage at the side marker.

Here’s a video of the led strip now.
Power/ground from led box to foglight pigtail.
Signal wire to corner amber light.

Do any of you think the led strip flashes too fast or slows down at certain times?
I can’t really notice anything like previous videos.
You can also see what I mean when I say the corner light and strip don’t flash together.


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Thank you for the help everyone.
I finally installed these this past Sunday.
In the end, the strips needed at minimum 12V to work properly. I did not notice any issues running them at higher voltages.
The description from the seller really had us running around!
The signal wire for the turn signal/flasher works fine with 1-10V.

I made a video of the install.

The only issue I see now, I was always working on this project after work, when it was already dark. I installed them during the day and the led light is almost none existent during daytime driving.