Detroit Diesel — Rotating Rectifier Assembly (RRA) Test Procedure
Testing & diagnosis · Rotating rectifier assembly/varistor
From a Detroit Diesel service manual — check it applies to your exact model before use.
Procedure
- Disconnect exciter armature and rotor main field winding leads from the RRA; keep leads separated.
- Use ohmmeter on R x 100 scale to check resistance between RRA diodes.
- Low resistance one direction and high the other indicates good diode; replace diode plates if any of six diodes differ.
- Replace varistor if evidence of heat damage; replace diode assembly hub if damaged.
Tools required
- Ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Source: Detroit Diesel service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.