headlite question

At the expense of sounding like Captain Obvious, if you have a good 12 volts (or so) of current going to a known good headlight WITH a good ground, the headlight will work. How did you test the ground? I had a similar problem when I put my 69 Barracuda back together a few years ago. It turned out that the ground wire from each headlight pigtail ran to a wire that was screwed into the firewall. That screw/eyelet combination was not making good contact. First, test the headlights with 12 volts. Then test the ground more thoroughly. Like I said, 12 volts to a properly grounded good headlight has to work.