10-01-2025, 10:24 PM
Regarding LED stop and tail lamps. The ones from some suppliers consist of a single LED, with two different value series resistors to give a high current for stop and a lower (= dimmer) current for tail. That's all fine and dandy, but there is an increased chance of backfeeding and odd effects with this simple setup, especially if the car has a mix of LEDs and filament bulbs. In my setup, I resorted to adding series diodes in the wiring to prevent back feeding.
Another effect is that if bulbholders are not in the first flush of youth, their slightly tarnished connections may work fine with filament bulbs as the higher current tends to "wet" the contact. I'm uncertain of the exact mechanism, but possibly a bit of micro-arcing burns through the tarnish. If you use lower current LEDs contact may become less reliable, especially if the "bulbs" have hard nickel contacts rather than the traditional more accommodating soft solder. The cure is thorough cleaning or using new holders.
Another effect is that if bulbholders are not in the first flush of youth, their slightly tarnished connections may work fine with filament bulbs as the higher current tends to "wet" the contact. I'm uncertain of the exact mechanism, but possibly a bit of micro-arcing burns through the tarnish. If you use lower current LEDs contact may become less reliable, especially if the "bulbs" have hard nickel contacts rather than the traditional more accommodating soft solder. The cure is thorough cleaning or using new holders.