Bench Testing a Valeo Alternator

[glassescase]

I am having problems bench testing an alternator. It is a 2 pin 3 wire alternator, I think its called 3 wire

I have the B post of the alternator connected to the positive of a battery. The chassis of the alternator is connected to the negative of the battery.
If I test from the B post to what I think is the L pin I get 12 volts. From YouTube videos, if I connect a light bulb from the B post to the L pin, it should light up.
It doesn't. I fitted a new slip ring, if I have this reversed, top ring goes to wire A instead of B and bottom ring goes to B instead of A what problems would this cause?

Any idea why, even though I have 12v the bulb which is only 2.3 watt it wont light? The bulb does work


thanks glassescase