It's pretty much a given that there is a wiring problem. I can't remember exactly how the lights are wired, but I would try first hooking a wire from the battery ground to the bad light, and verify once again that your ground is not bad. Then I would try just splicing into the other light's high beam wire, and see if that fixes it.
Good luck,
Terry
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'85 CJ-7 - 33s, total of 4.5" lift,
TFI ignition, plus more.
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