T5 Millennium electrics

[Jay71]

Can anyone tell me what the black box does on a T5 Millennium? It's located under the horncast at the bottom.
This scooter has issues with the horn not working when main lights are on! Removed black box and horn worked
But went from decent sounding horn to the classic duck sound! Also later blew
Most of the scooter's bulbs! There is no battery fitted or electric start on this model.

[Jay71]

[Jay71]

Through the power of social media, it's a horn rectifier!

[george4422]

Hi, I have just stripped, bead blasted, painted and rebuilt a T5 Millennium, the engine runs fine, but complete lack of all electrics (lights, indicators, horn...) I've checked the blue wire going into the regulator and plenty of power there. I fear the horn rectifier may be the issue... any other suggestions or help would be greatly appreciated!