Third brake light strobe?

[flip7]

I tried installing a 3rd light flasher/ strobe for my 2013 Jetta (w./ OEM LED lamp) without success
The module is called LSC-100A (ebay and Amazon is full of them)
http://www.ebay.com/itm/161805196247?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
Issue is that it works fine if the engine is Off, but is no longer working when the engine is ON.
I thought is because of the higher voltage when charging, and tried reduce it with one or two diodes.
Still, when I start up the engine, the rig stops working...
have you had any similar experience?
Thank you

 

[erbilabuc]

what is voltage, wattage and ohms to the light with engine off and same question with engine on.

 

[flip7]

So the lamp takes 0.85A @12V that is ~10W

Voltage at the flasher module input is 12V with engine turned off, and some 13.5 when engine is running.

Ohms to the light - not sure is a worthy measurement since it is a LED module which likely has some light electronics in it too.

I tried with two similar models for the flasher module, and both behave exactly the same.

 

[Ol'Rattler]

Sometimes there are garbage made in China things you might buy that are best just thrown in the trash before they have the opportunity of malfunctioning and at worst, damaging your car.

Seriously, we need some sort of trade agreement with China that will penalize Chinese companies if they sell products that do not perform and last in a reasonable manner.

 

[flip7]

After getting my hands on an oscilloscope, the definitive answer is that the third brake lamp is a PWM (pulse width modulated) at 100Hz with a 90% duty factor. VW does this to enable light adjustment for the LEDs in the car.

also here:

http://forums.vwvortex.com/showthread.php?5210703-How-VW-s-lighting-module-drives-the-bulbs

Next phase of my project will be so see if the duty cycle of the PWM can be adjusted with Vagcom to 100%

I tried installing a 3rd light flasher/ strobe for my 2013 Jetta (w./ OEM LED lamp) without success
The module is called LSC-100A (ebay and Amazon is full of them)
http://www.ebay.com/itm/161805196247?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
Issue is that it works fine if the engine is Off, but is no longer working when the engine is ON.

Thank you

 

[Ol'Rattler]

Wow. I'm all in. Don't pitch that strobe just yet. Anything I can learn about PWM and other aspects of how a digital car works I'm all ears.

Keep us informed on what you find.

 

[Tech20]

Flip,
Would it be possible to use a capacitor to smooth out the PWM signal? I'm not sure if it would affect the brake circuit as I haven't seen any schematics and don't know much about my car yet. There would be a short charging but at 100 HZ I would think it would be negligible in the big picture. Possibly a resistor / dummy load to the negative and a standalone ground might be needed if the car requires voltage back from the light? Hopefully You make progress on this.

 

[flip7]

Flip,
Would it be possible to use a capacitor to smooth out the PWM signal? I'm not sure if it would affect the brake circuit as I haven't seen any schematics and don't know much about my car yet. There would be a short charging but at 100 HZ I would think it would be negligible in the big picture. Possibly a resistor / dummy load to the negative and a standalone ground might be needed if the car requires voltage back from the light? Hopefully You make progress on this.

The solution is:

from the third brake light harness positive pole place series 1N4007 Diode followed by a 660uF/25V capacitor (between diode's catode and GND)
Now you connect the flasher In + to the Diode's Cathode.
The diode prevents the capacitor load to go back to the BCM module during the PWM off cycle

If someone needs the schematics, PM me. I don't know how to upload an image to this forum.

 

[Tech20]

Good Job Flip. This is a great modification for safety.

 

[Antsrcool]

Not sure what or why your strobing. But I'm an emergency vehicle upfitter. What you need if I'm hearing you correct is a shome led flasher stt. Stt stands for stop tail and turn. There about 28 dollars online. http://www.vehiclesafetysupply.com/...turn-tail-led-flasher-11-1005-stt-p-2020.html