Modern Vespa

Is my HS1 headlight AC or DC.
Thanks

If the headlight comes on:
- when you turn the ignition key on: it's DC
- only after the engine starts: it's AC

I thought that AC corresponded to Alternating Current and DC a Direct Current ... I believe that all the electrical system of the scooters (except the older ones) is Direct Current, if that's what you mean ...

Smaller scooters with small batteries often have a specific winding (a phase, so to speak) from the stator that goes directly to the headlight, bypassing the regulator/rectifier. That output is AC, which is fine with incandescent bulbs but can be problematic with LED replacements.

This is so the relatively high drain of the headlight (35 watts, or more) doesn't reduce the cranking power of the little battery.

I was installing a signal dynamics headlight module. Sweet simple design. But when done I got nothing. They said the module does not work on AC. Never occurred to me my Vespa was AC. Bummer.

And now, can I return it? We shall see.

... you never stop learning something ...
Thanks for the clarification.
PS: on Yamaha scooters (at least on X Max and Tricity) when you press the starter the headlights go out momentarily.

Signal Dynamics has 100% money back guarantee. So back it goes. Too bad because theirs was really plug and play. Nice design.

Except newer scooters don't turn on the headlight until the engine is on.

Not necessarily! Many Piaggio bikes (GTS300 included) only fire up the headlights when the engine is running.

Pretty sure it's true of all 50cc scooters like the OP's.

Are there larger modern scooters with AC headlights? All the 150s and larger I've messed with are DC.