On one car, I experimented and added an extra incandescent bulb in series and upstream of the rest and stashed the bulb out of sight in a blackened container and that worked even better. All I can say, I did this on an "engineering based gut feeling" and it worked! I want to clarify that I did only purchased the natural white/clear LEDs from Jules via Sven and the red, green, and blue color ones I had handy from another project and from another source. I also did opt to use the incandescent only for the generator/alternator indicators. I also played around off the car using some small wire jumpers and a spare light switch and was able to duplicate the dimming on my work table; the results were the same.
Maybe (if he chimes in) Jules's complete kit has a "special" LED that mimics the incandescent bulbs; I do not know since I only bought enough of the clear ones and not the kits. By the way, I tried to dim LEDs from another supplier and they just did not dim at all and were only either "off" or "on" with the light switch dimmer function.
Good luck!
