Cummins/Onan — Brush Contact Maintenance
Maintenance · Brushes, commutator and slip rings
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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Before you start
- Never use emery or carborundum cloth or paper.
Procedure
- Every 200 hours or once a month clean the commutator and slip rings with a dry, lint free cloth.
- Heavy deposits or slight roughness may be remedied by careful sanding with #00 sandpaper held flat with a wooden stick while the generator operates.
- Do not remove the brush rig or end bell when installing new brushes; remove the end bell cover for access.
- Replace brushes when worn to 5/8 inch in length.
- Install commutator brush with the low side of the beveled top toward the spring-plate side of the guide.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Replace brushes at 5/8 inch length
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.