Starting System & Charging System (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 ohm or less only in the direction from the diode lead to heat sink.

Fig 1: Checking Positive Diode
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 ohm or less only in the direction from the heat sink to diode lead.

Fig 2: Checking Negative Diode
Courtesy of SUBARU OF AMERICA, INC.