04-06-2020, 08:51 AM
to avoid wasting any more time: I've fiddled with the way the green wire was mounted and now it's illuminating in a predictable manner. There must have been some tomfoolery around how I had it clipped to the tail light housing. You see, I didn't want to solder anything or make any permanent connections until i was sure everything worked correctly, so i just sort of clipped the green wire to a bolt that held the bulb assembly into the steel housing of the light fixture. this produced the results i gave above. when i moved the green wire onto one of the bolts that attached the fixture to the fender (using a makeshift ring terminal), the bulb began to behave correctly. now the lower bulb filament is always on while the upper bulb filament flashes with the brakes. i soldered the rest of it together and have it all mounted now. done deal.