> Jumper wire to dim lo beam did not work, but the ground had to be
> good because the hi beam (on the same circuit?) worked.
Bill, any chance your headlight bulbs are not identical ? You mentioned
having H4 bulbs, could one be a higher power version than the other ?
Incandescent bulbs can do very strange things when a ground is open. Part
of the reason is because the filament's 'cold' resistance is so much lower
than it's 'hot' resistance. With no ground to one headlamp, the unlit
filament in the other lamp will act as a ground to both filaments in series
in the ungrounded headlamp. Depending on the relative cold resistances,
that may or may not make the ungrounded headlamp light.