ok.... i stopped.... kind of...
...did you just call me stupid?
ok, so investigated the bulb. i can't figure out how i would measure voltage in the clusterboard with the ignition on, so i figured the easiest way would be to swap in the spare cluster i have, which i did.
in both clusters the bulb works as it is supposed to, and is bright, just as bright as all the others. it comes on before and during start then shuts off, also flashes (once) on shutdown.
i went for a testdrive with the spare cluster in and had the same poor charging results.
so can we rule out the cluster / bulb / resistorbehindthebulb ?
hmmm.... remember this?
here's a better photo
here's the etm again, with the PO's splices marked with caffeine-laden arrows.
what am i doing still in front of the computer?