I have a ceiling light which has gone out and not because of light bulbs burnt out. Have taken down the light and all connections look good. When the light is hanging I can put a bulb in and the light turns on. When I reinstall the ceiling light (accomplished through a centre bolt and nut in the base of the light which you tighten to hold the ceiling light in place). Now that the nut has been screwed into place, the light won't go on. Now if I place a rubber washer between the centre bolt and the nut so that I can still screw the bolt into place but it is isolated from touching the ceiling light base, the light will go on.