I need to replace my 12VDC (bulb based) break lights but I am unable to find a 3 functions light (Running/Brake/Off) with the same specs. I did however find a 2 functions light LED (ON/OFF) with the exact same dimension.

I want to install the 2 functions LED based light brake in my car but using it as a 3 functions light.

I thought of building a small circuit that gives the light max 50% on each rail using a resistor and adding a potentiometer for configurable dimming.

So when the car is running the LED light gets max 6V via rail1, and when I brake, it get max 12V via both rail1 + rail2.

Does this approach make sense? Can you suggest anything else?

If it does, I have no idea how to build that circuit starting from my 3 wires, as simple as it sounds :/

Thanks for any help.