Bench Testing: Diode

WARNING: This page is about a different car, the 2004 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.

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.

Check for continuity between the diode lead and positive side heat sink. See Fig 1. The positive diode is in good condition if resistance is 1 ohms or less only in the direction from the diode lead to heat sink.
Check for continuity between the negative side heat sink and diode lead. See Fig 2. The negative diode is in good condition if resistance is 1 ohms or less only in the direction from the heat sink to diode lead.

Fig 1: Checking Positive Diode

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Checking Negative Diode

Courtesy of SUBARU OF AMERICA, INC.