Test alternator diodes - AR15.40-P-9301-02EW

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ENGINE 157, 272, 273, 276, 278, 642, 651 in MODEL 212

ENGINE 157, 276, 278 in MODEL 218

Connection scheme

Fig 1: Alternator Diodes Circuit Diagram - Connection Scheme

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Connect engine tester with oscilloscope (030).
Start engine.
Switch on low beams.
In this test it is not possible to assess the exciter diodes.
Assess diode harmonics at 3000 rpm (engine speed).
Harmonics of the diodes is OK (example)

Voltage peaks are possible but without meaning.

Fig 2: Diodes Harmonics Graph OK
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Harmonics when a positive diode is faulty (example).

Fig 3: Diodes Harmonics Graph (Positive)
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Harmonics when a negative diode is faulty (example).

Fig 4: Diodes Harmonics Graph (Negative)
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