I'm not that familiar with the 280Z schematics but the headlight wire colors are the same. ZANTHUS, the white, 3 wire switch on the turn-signal assembly, is the headlights HI-LO switch. Make sure the the center wire is getting contact to each of the side wires with each flick of the switch. At the plugs, (Round white 3-wire plugs) either in the engine compartment or in front of the radiator, the red/white is the hi beam wire and the red/black is the low beam wire. On the right headlight plug the solid red is the power wire, on the left headlight plug the red/yellow is the left headlights power wire. The lo and hi beam wires are negatives when activated. Your BEST diagnostic plan would be to turn on the HI beams, and start pulling relays around the car, one at a time, till the highbeams go out. When they go out, you'll be in the right area to find the low beam relay. replace the lowbeam relay with the HI beam relay and see if the lo beams work. If they do, then find another relay (at Nissan or local auto parts store) and replace the bad one. My Headlight relay upgrade harness will do NOTHING for a system that does'nt work properly to begin with. The fuses in the fusebox are for Left and Right headlight, not hi and lo beam. JFYI. let us know what ya find. Dave.