Im not sure how the indicator circuit works, theres a hazard light relay but I'm sure the clicking sounds like its coming from the instrument cluster?
The lights on buzzer made me think though, my old Mk3 one used to work but my 16v one works randomly. Theres a gong in a footwell of most 3 series and Z4 BMWs and they have a decent 'lights on' warning tone. Never thought to try, but I have a spare one and will give it 12v at work next week and see what happens. Im sure the Mk3 just has a buzzer and operates like this.