My '67 Fury has stopped charging for some reason. Last year I converted it to a solid state voltage regulator and the altenator with the two field terminals. It has been very well until now. The battery is a little over a year old. I had to use a booster pack to start and when running at a fast idle, the amp gauge shows only a slight charge. At the battery terminals I get 12.5 volts at fast idle. The headlights are also dim. Any ideas on how to locate the source of the problem will be greatly appreciated. Thanks.
John