'91 GTD gauges into '84 passat TD. Rev counter not working

[carraca]

Hi,
I am installing GTD cluster in a '84 passat TD so I finally have a tach, but I can't make the rev counter work.
I have to say that I made a mistake with the two green wires and contected the green wire of the tach to the blinker (which is 12v constant) instead of the W terminal.
I heard a buzzing sound from the cluster and inmediately disconected it.
Rewired it but the tach is dead.

Did I fried the tach? How can I check it?

Also, how do I check if the W terminal is providing a signal?

There are three spare wires in the GTD I don't know where to hook. Two white/red at possitions 2 and 9 and a purple one in possition 7. Should I contect the three to ground?

Thanks!

Marcos