Testing Diode Trio
WARNING: This page is about a different car, the 2000 Subaru Impreza and 2000 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
To check diode trio, remove diode assembly from rear cover. Using an ohmmeter, check each diode for continuity. Continuity should be present in one direction only. If continuity is present in both directions, or continuity does not exist in either direction, diode trio is faulty. If any diode is faulty, replace complete rectifier assembly.