The alternator can easily be tested without fitting, by the use of a battery, some bits of cable, a 12v 2 watt bulb and an electric drill.
Connect the B+ stud Terminal direct to the battery positive, connect the battery negative to the body of the alternator, and the D+ blade terminal to the battery positive via the 12v 2w bulb. Run the alternator up with an electric drill with an appropriate socket on the end to drive the alternator via the pulley nut. Check the battery voltage is around 14 volts and the bulb light goes out.
Going back to the dynamo, perhaps I'm too late in this instance, but for others who may read this; provided the bearings, brushes, brush springs, end float are OK and the copper windings (field coils and armature) are OK (not broken or burnt out) nearly every VW dynamo can be started. Due to today's H & S legislation the likes of Haynes and Bentley could not go to print. However, if anyone wants to try the well tried and proven method of starting a dynamo, please email me for details. peter @volksgoods. co.uk without the spaces.
Peter Good