12Volt or 6, we'll stay with the 12volt system for now
As above, think from memory they use a small 2 bobbin regulator? And its external from the dynamo.
How do you know when its charging? Don't depend on the warning light for fault finding as its controlled by a set of contacts in the regulator (I think).
Think you jump the DF (dynamo field) wire to + 12 volts and if it start charging you know the dynamo is working. Then its down to wiring or regulator. Some of those had a bad ignition switch, but I think you will find the charging light goes dim when it should go off.
it is 12v i have a volt gauge fitted in tank to tell me voltage .the only thing i can think of is the speedo whent wrong and the earth system is connected below clock ,i have reconnected earth though so this should not be problem.
Links
http://www.vw-resource.com/generator.html#charging[/QUOTE]