Bench Testing: Diodes

Using an ohmmeter, check continuity of all diodes in both directions. See Fig 1 and Fig 2 . 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 - Positive (Hitachi)

Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 2: Testing Alternator Diodes - Negative Side (Hitachi)

Courtesy of NISSAN MOTOR CO., U.S.A.