Originally Posted by martysmartie

The light gets it's power via the ignition switch the same as the rest of the warning lights, the earth is the blue wire which goes on the back of the alt when stationary this acts as an earth hence the light illuminates, it also excites the field windings in the alt which in turn starts the charge process, when charging the terminal where this wire connects changes so it has the same power at the alternator output terminal and thus the bulb is now receiving two lives and so the bulb extinguishes.

I think I know exactly what you have done it's just come to me, you have connected this wire to the W terminal, this is an 8V output for electric chokes or tachos on diesels which explains it lighting while the car is running (I am tired LOL ), have a look on the back of the alt for another terminal should be D connect this wire to here and I can gurentee this will sort your problems.

That being said if the car is revved to around 4000+ RPM it should start charging.

Martin