Bench Testing: Diodes

Using an ohmmeter, check continuity of all diodes in both directions. See Fig 1-5 . Ensure continuity exists in only one direction. If continuity exists in both directions, diode is shorted. If continuity is NOT present in either direction, diode is open. If any diode is defective, replace entire diode assembly. See TESTING ALTERNATOR DIODES  table.

Fig 1: Testing Alternator Diodes (G20 & Q45 - Hitachi)

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Fig 2: Testing Alternator Diodes (G20 & Q45 - Hitachi)

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Fig 3: Identifying Alternator Diode Test Points (G20 - Mitsubishi)

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Fig 4: Identifying Alternator Diode Test Points (M30 - Hitachi)

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