Charging system

Do you have a digital multimeter? They don't cost much. An analog meter is even less. Eveything off, place leads across battery posts, an analog meter is polarity sensitive, hook it up correctly. The generic spec for a full charge is around 12.6 volts. Then start the engine, take second reading across battery posts, the second should be higher than the first if charging system is working. You can also take reading at alternator bat terminal, if that reading is higher than it is across the battery posts, engine running, then there is problem with the wiring circuit from alternator to battery.

The alternator has to receive excite voltage, L terminal, or even a good alternator won't work.