Starting System & Charging System (H4SO): Generator: Inspection: Diode

CAUTION: There is the possibility of damaging the diodes if a mega-tester (used to measure high voltages) or a similar measuring instrument is used. Therefore, absolutely never use in this test.

Check the positive diode
Check the continuity between the diode lead and positive side heat sink. If resistance is 1Ω or less only in the direction from the diode lead to the heat sink, the positive diode is normal.

Fig 1: Checking Continuity Between Diode Lead And Positive Side Heat Sink
Courtesy of SUBARU OF AMERICA, INC.
Check negative diode

Check the continuity between the diode lead and negative side heat sink. If resistance is 1Ω or less only in the direction from the heat sink to the diode lead, the negative diode is normal.

Fig 2: Checking Continuity Between Diode Lead And Negative Side Heat Sink

Courtesy of SUBARU OF AMERICA, INC.