HERE's Jerry's comprehensive Tech Tip for the charging system.
The service manual is also a good resource and includes info on how to adjust the voltage regulator, although that shouldn't be messed with until other troubleshooting steps are taken. If a regulator has set idle for a long time, and the battery isn't getting charged, running a business card thru the contacts will clean them up and may get it working again. Just don't tweak anything in the process.
