Fitting a Revv Counter - C14NZ find terminal 15 on ignition

[McPoel]

Hello Forum,

Trying to fit a tacho. It's a universal one, got positive & negative power cable and one that goes on terminal 15 of the ignition coil. The engine got contactless ignition. So no distributor and sepapate coil where one could connect to terminal 15. There are 4 wires that go into the ignition coil via a multi wire connector. I measured and found out the black (bottom position when connetced) one appears to have 12V when ignition is on. Hence I concluded it must be terminal 15. But having connected the tacho to it, it does not work at all. Does anyone know what which wire is for? Might help.
There is an article in the FAQ but I cannot apply this here as acc to my instructions the tacho just needs one cable at terminal 15 (apparently then counting 12V-0V alternations).

Haynes doesn't show the function of the wires unfortunately.

Thanks in advance,
Stephan

PS: I've taken a picture of the connector but apparently there is no way of adding an attachment here. So hope my description is good enough.

[McPoel]

...can't edit the above but here's a link to the above mentioned photo: http://sh08.webatu.com/bilder/Corsa.jpg