I do have a radio.
I found this link to the MBZ Ponton site about polarizing a generator:
Polarizing a Mercedes-Benz Ponton Generator © www.mbzponton.org
I attempted to polarize my generator twice according to the steps but could not get the GL light to extinguish. Next I checked the link referenced in the Ponton article and tested my generator by itself. Unencumbered from the regulator, it seems to put out 30+ Volts as the engine revs.
Would appear that my generator is ok but the regulator may not be.
Will be searching for regulator tests (it was fine before the dismantle)
