Starting/Charging Systems (H4SO): Generator: Inspection: Diode

CAUTION: Never use a mega tester (measuring use for high voltage) or any other similar measure for this test; otherwise, the diodes may be damaged.

Checking positive diode
Check for continuity between the diode lead and positive side heat sink. The positive diode is in good condition if resistance is 1 Ω or less only in the direction from the diode lead to heat sink.

Fig 1: Checking Continuity Between Diode Lead And Positive Side Heat Sink
Courtesy of SUBARU OF AMERICA, INC.
Checking negative diode
Check for continuity between the negative side heat sink and diode lead. The negative diode is in good condition if resistance is 1 Ω or less only in the direction from the heat sink to diode lead.

Fig 2: Checking Continuity Between Negative Side Heat Sink And Diode Lead
Courtesy of SUBARU OF AMERICA, INC.