Test diodes of generator - AR15.40-P-9301-02I

Connection diagram 

Fig 1: Generator Connection Diagram

In this test it is not possible to assess the exciter diodes.

1. Connect engine tester with oscilloscope (030).
2. Start engine.
3. Switch on low beam.
4. Assess diode harmonics at 3000 rpm (engine speed).

Harmonics if diodes are OK (peak stresses possible but of no significance) (example). 

Fig 2: Identifying Diode Harmonics OK

Harmonics if a positive diode is defective (example). 

Fig 3: Identifying Harmonics - Positive Diode Defective

Harmonics if a negative diode is defective (example). 

Fig 4: Identifying Harmonics - Negative Diode Defective