1988 750, left front side marker light inoperative. Changed bulb, no light. Changed fuse, no light (all others work). Did a voltage check of the connector and bulb socket, 10 VDC with engine off (same voltage at other side marker locations). Swapped out bulb holder from front to rear to isolate a bad holder, front holder works fine in other locations, other holders do not work in the front location. Swapped bulbs, front to rear, bulbs work in oter locations, not left front. All parking and other lights work. I am at a loss here, I have voltage but no light.

check your ground, if you havent already.

I have checked the ground, it is common with parking light which works and the circuit checks for continuity, this is weird.