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

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Connection diagram

Fig 1: Alternator Diodes Connection Diagram

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Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

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

Connect the engine tester with oscilloscope (030).
Start engine.
Switch on low beams.
Assess diode harmonics at 3000 RPM (engine speed).

Example: Diode harmonics in order (voltage spikes possible, but not significant)

Fig 2: Waveform Display - Diode Harmonics In Order

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Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Example: Zero line, in the event of a line interruption or a defective fuse.

Fig 3: Waveform Display - Zero Line In Event Of Line Interruption Or Defective Fuse

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Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Example: Harmonics, if a positive diode is defective.

Fig 4: Waveform Display - Harmonics if positive diode defective

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Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Example: Harmonics, if a negative diode is defective.

Fig 5: Waveform Display - Harmonics If Negative Diode Defective

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Courtesy of MERCEDES-BENZ OF NORTH AMERICA.