After cleaning the fog lamp lens enough to be encouraging, I made an LED “bulb” from four WS2812 RGB pixels:
The small threaded hole has an M3 setscrew to let the brass post slide up & down to adjust the LED position inside the fog lamp’s reflector.
Despite my poor experience with the PCB-based WS2812 LEDs, the strip-mounted ones have been ticking along in the hard drive platter lamp basically forever, at least after I tamped down the heat problem.
The brass hex rod has plenty of thermal conductivity, particularly clamped into an aluminum disk connected more-or-less well to the fog lamp’s base.
The two short wires linking the two LED strips (the purple wire is data into the first LED) hold them in place around the hex, despite their desire to straighten out, pull free of their adhesive, and fall off.
The general idea was to put the LEDs at about the same level as the halogen bulb filament, thereby spreading enough light to fill the reflector housing:
I drilled a hole through the hex as a cable “conduit”, turned the end into a nice rod, then machined a stub of aluminum to fit:
A pair of slots milled along the sides of the aluminum disk fit the housing’s locating features:
Nissan used an elaborate spring latch to clamp the halogen bulb’s sheet-metal base in place, but its 50 mil wire didn’t have nearly enough give for my chunky aluminum disk. My version of a spring latch came from a length of 24 mil music wire, which definitely beats the epoxy I was planning to use.
Heat transfer seems to be a non-issue, as the LEDs get barely warm to the touch. Until they drop dead, I’ll assume it’s all good in there.
Two screws hold the lens in place, but the collision seems to have stripped their grip on the plastic and they didn’t un-screw:
Jamming a utility knife blade under the screw head and prying upward while turning the screwdriver persuaded them out of their sockets, after which the lens popped out of its form-fitted silicone gasket with surprisingly little effort:
The lamp spent a week or so beside the road, out in the weather, and shipped a few drops of rainwater through the rectangular hole under the spring latch anchor. Some delicate cotton-swab action removed most of the grime without too much damage, but the reflective film on those corrugations won’t ever be the same again.
Now it’s just a simple matter of software …