Series 2 alternator exciter wire

i have just changed engines in a 1962 series 2a, and somehow i lost the exiter wire,but on fitting a new one i seem to be getting 12 volt from the alternator small conection, i understood that it should feed 12 volts to the alternator, am i right in thinking this?, and would any 12 volt switched feed do for the exiter feed, fed via the charge light?

Once the alternator is excited the terminal will give 12V thats why the light goes out.
ie 12V at each side of the bulb so no current flow.

i havn't had the engine running yet still waiting for head to come back,so with the main battery wire connected, i am getting a 12volt reading from the small terminal on the alternator

I would suspect the diode pack in the alternator is faulty. Quite cheap to replace.
Have a look at the internal diagram in thios link
http://www.tb-training.co.uk/MarineE08.html

Hi, Blackburn, yes you are right, swapped alternators today and have ignition light now, but thanks for your input