How does the headlight buzzer work?

[Dino]

Can someone explain how this gizmo works please? And how to test it out of the car?

[Dino]

I still don't know how it works, but I installed it and it buzzes!

[b5blue]

Are your headlights on? 

[Dino]

 

Yes, it only buzzes with the lights on.

[Nacho-RT74]

On 3 gens It gets positive from parking lights ( yes, is actually a lights on buzzer and no just headlights ) and negative from driver's side door jam switch.

Would need to check why 3 prongs on earliers. As soon I can will check diagrams to analize it.

[Dino]

Thanks Nacho!