It's all about Resistance. Resistance causes heat. Resistance in your system comes from aging wires, contacts and connectors. The 240Z's wires were too small of a gauge to begin with. Then the Z ended up lasting 40 years. Hi amperage, thru 40 year old wires causes resistance. Get it? Thought you would. Now the solution. Pull each and every connector in the headlight circuit, clean them and make sure they are tight and making the best connection possible. There are chemicals out there that will eliminate the corrosion and expose a clean metal surface.. Can't remember the name at the moment but I'm sure someone will chime in with the right answer. When I say "Each and Every connection" That means, the Headlight connectors at the bulbs, the ones in front of the radiator, inside the passenger side dash area, the fusebox (power in and out) the fuses, the combo switch contacts and connectors. The HLH will take your weak signal in front of the radiator and activate the relays, which get their power directly from the battery via a fused 10 gauge power wire, New connectors and terminals. So the only weak spot after installing an HLH is the pigtail harness between the connector at the bulbs and the new harness. Hope that helps, Dave