Alternator Disassembly and Inspection

1. Rotor Inspection
   After correcting any contamination or roughness on the slip ring surface with sandpaper, check continuity between the slip rings using a circuit tester set to the resistance range. Continuity must be present.
   Next, check insulation between the slip rings and the rotor core using a megger. Contamination such as brush wear powder adhering to the slip ring surface may cause insulation failure; clean and correct as required.
2. Stator Inspection
   Using a circuit tester set to the resistance range, check continuity between each phase lead wire from the stator and the neutral point (N terminal). Continuity must be present.
   Subsequently, check insulation between the stator windings and the stator core using a megger.
3. Diode Inspection
   Using a circuit tester set to the resistance range, measure resistance between the B terminal or E terminal and each diode terminal. Perform measurements with the tester probes in both polarities:
   • Positive (+) probe on the B or E terminal and negative (–) probe on the diode terminal.
   • Probes reversed.
   • A diode is considered serviceable if the difference between forward and reverse resistance values is sufficiently large.
4. Brush Inspection
   Verify that the brushes move smoothly within the brush holders by lightly pressing them with a fingertip. If movement is impeded by dust or brush wear powder, clean and correct as required.
   Measure the brush length from the end of the holder using a vernier caliper. Replace brushes if wear exceeds the specified limit.
5. Bearing Inspection
   Rotate the bearings lightly with the fingers. The bearings must rotate smoothly without roughness, abnormal noise, or excessive play. Replace bearings if any defect is found.

• Performance Test (Using Alternator Tester)
  Conduct the following tests with an alternator tester:
  • No-load rotational speed test
  • Output rotational speed test
  • Output voltage test
• Oscilloscope Test
  Set the oscilloscope to the specified range. Connect the probe to the alternator B terminal and the ground lead to the E terminal.
  Start the engine and observe the waveform at idle speed. If the stator windings and diodes are normal, a proper voltage waveform will be obtained.
  Under load conditions, the waveform may fluctuate due to voltage regulator control. Wait until the waveform stabilizes, then reconfirm.