Cummins/Onan — Testing the Armature for a Ground
Testing & diagnosis
From a Cummins/Onan owner's manual covering: 4UF-3N41, 4UF-3N42, 7UF-3N41, 7UF-3N42, 7UF-3N61. Check it applies to your exact model before use.
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Procedure
- See that all brushes are lifted out of their holders.
- Use a continuity type test lamp set; place one test prod on the commutator and the other on a bare clean part of the frame or shaft.
- The test set lamp should not light. If it lights, the armature is grounded.
- Test the slip rings in the same manner; replace with a new armature if grounded.
Tools required
- Continuity type test lamp set 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.