Cummins/Onan A15 — Testing the Rotating Rectifier Assembly
Testing & diagnosis · exciter rectifier bridge
For the Cummins/Onan A15, from the Cummins/Onan service manual.
Applies to: Cummins/Onan DGBB, Cummins/Onan DGBC, Cummins/Onan DGCA, Cummins/Onan DGCB, Cummins/Onan DGCC, Cummins/Onan DGDA, Cummins/Onan DGDB, Cummins/Onan DGEA, Cummins/Onan DGFA, Cummins/Onan DGFB, Cummins/Onan B and C Series diesel engine
Before you start
- Layers of dust can cause diodes to overheat and fail.
Procedure
- Disconnect diode pigtails from terminal posts.
- Measure resistance between each diode pigtail and its mounting plate; reverse probes and repeat.
- Resistance should be high in one direction, low in the other; replace diode if high or low in both directions.
- When replacing, apply heat-sink compound under diode head (avoid threads), torque diode to 36-42 in-lbs (4-4.8 Nm) and pigtail terminals to 24 in-lbs (2.7 Nm).
Tools required
- ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- diode torque 36-42 in-lbs (4-4.8 Nm)
- pigtail terminal torque 24 in-lbs (2.7 Nm)
Full service-parts list: Cummins/Onan DGBB →, Cummins/Onan DGBC →, Cummins/Onan DGCA →, Cummins/Onan DGCB →, Cummins/Onan DGCC →, Cummins/Onan DGDA →, Cummins/Onan DGDB →, Cummins/Onan DGEA →, Cummins/Onan DGFA →, Cummins/Onan DGFB →
Source: Cummins/Onan 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.