This is simple and self-evident to most anybody with a soldering iron but here we go….
First a primer on headlamps. Rated at 55 watts, an H4 lowbeam headlamp consumes around 55 watts, I guess, which is something like 4-5 amps. With a 240 watt alternator and with barely any charge below 2500 rpm, goofing around in the city, prior to cranking on a cold morning, or when your electric system is failing, it would be good to be able to switch off the lamp. Moreover, the parking lamp is on all the time and can make-do for a substantial part of the safety and regulatory issues, especially in the daytime. Finally, if you need some lamp action, you can always flick on the highbeam the two habitual ways which are unaffected by this mod.