ummm,,errrr ,flame me now,,have you access to a rec/reg from say a boldor??or some other electronic unit?,,truly,,after all these years,,the factory ones can develop these dramas,,now matter how reliable others have had these things be,,they do do this stuff,,temperature sensitive 35 year old rectifier???,,i dont know,,if you can swap it over easy try it.,if the field and stator test true??i think its a good try.