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Hello guys.

Here is my project. I got a car with aftermarket taillights. I was planning on replacing them, but I thought I would give it a try to fix them.

Why spent 700 USD on new lights... since LEDs do not tend to fail.

I was right in the part LEDs live long. I tested all of them and each and everyone lit up. Turns out the controller/module whatever one would call it, failed. It provided a bit of current only to a few of them making me believe they failed.

Problems I have - no clue what LED chips those are. They are square, clear, glow in red. They are chained 4 pieces in series, overall 5 chains.

Those LEDs are dual purpose - parking lights and brake lights. I believe lower voltage would be applied to limit the light intensity, right? Full power for the brake light.

My thinking is. Instead of the controller I can use two bucks - one for parking and one for brake lights. I kind of know that I should use a resistor... right?

One buck would provide say 13 V for brakes (almost as pass through), while the other would be set at about 7-8 V for parking. It comes from my test.

Since there are 5 chains, 3 of them would be for parking, while all 5 will be active for brakes. I think it would not make a problem to "back feed" the 7 V one with 13 V.

https://smile.amazon.com/gp/product/B08S2TDR8Q/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

This is what I got.

The light is something like that: https://www.carpartstuning.com/led-taillights-suitable-for-porsche-boxster-986-96-04-black-rpo01llb/4971-2/

And the LEDs look like that: https://www.globalsources.com/Through-hole-LED/Piranha-LED-1163428017p.htm#1163428017

so basically - is my idea correct?

Problems I have is to know the current and how to pick the resistor. Or something more I did not think about...

Not sure how to add a circuit to already existing question. https://www.circuitlab.com/circuit/7m97ybvc4vv9/car-brake-parking-led/