Cummins/Onan — Testing Rotating Rectifier Assembly
Testing & diagnosis
From a Cummins/Onan operator's manual covering: 250DFT-57R8, 300DFT-4R8, 300DFT-4XR8, 300DFT-5DR8, 300DFT-6DR8, 300DFT-7XR8, 300DFT-9XR8. Check it applies to your exact model before use.
Browse Cummins/Onan generators & specs →
Procedure
- Remove access cover from exciter end of generator.
- Isolate each of the six diodes before proceeding.
- Use an ohmmeter to measure resistance in individual diode. Reverse leads and repeat.
- A good diode should have high resistance one measurement and low when leads are reversed.
- Check all diodes in accordance with reverse measurement step.
Tools required
- ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Six diodes
Source: Cummins/Onan operator'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.