Voltage regulator

The voltage regulator is inside the Engine Computer and causes very little trouble. By far the most common cause of failure to charge is worn brushes inside the alternator. That can be repaired with a nine-dollar brush assembly.

Measure the three voltages on the alternator wires. You should find full battery voltage on the large output wire all the time. The engine must be running to measure the two smaller wires. One will have battery voltage. The other one should have less, but not 0 volts. Tell me what you find.