Cummins/Onan — Testing Rotating Rectifier Assembly (Diodes)
Testing & diagnosis
From a Cummins/Onan owner's manual covering: 290.0WF-54R, 290.0WF-54XR, 290.0WF-57R, 290.0WF-59XR, 330.0WK-54R, 330.0WK-54XR, 330.0WK-55DR, 330.0WK-57XR, 330.0WK-59XR, 350.0WF-4R, 350.0WF-4XR, 350.0WF-5DR…. Check it applies to your exact model before use.
Applies to: Waukesha L1616-GSIU engine
Procedure
- Remove access cover from exciter end of the generator.
- Isolate each diode by disconnecting one end from its connection point.
- Use an ohmmeter to measure resistance in the individual diode; reverse the ohmmeter leads and repeat.
- A good diode should have a high resistance value one way and a low value when leads are reversed; replace if not good.
- Check all diodes in accordance with step 3.
Tools required
- ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Source: Cummins/Onan owner's 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.