How and where are you taking the voltage readings. Reading from battery post and from charging lead to neg battery post
What was the model number of the alternator, as you know there are a lot of different ones Could not find a model # on alternator and it is back together now
Is it regulated or unregulated both had the built in diode
If it is regulated and the battery is fully charged it will not generate any power because there is no reason to do do so.We have tried it with dead battery (jumped off) and fully charged battery, same results
To test you need to put a load on the electrical system like a lamp.
An old headlamp works well.
How did you wire it into the machine ? Charging lead is connected to positive battery lead
Photo please.