Cummins/Onan — Brush Block/Slip Ring Service
Maintenance · Alternator brush block
From a Cummins/Onan service manual covering: C13 N6H, C13N6H, C17 N6H, C17N6H, C20 N6, C20N6H, RS13A. Check it applies to your exact model before use.
Applies to: Cummins/Onan C13 N6H, Cummins/Onan C17 N6H, Cummins/Onan C20 N6, Cummins/Onan RS13A
Before you start
- Make sure the brushes are aligned correctly with the slip rings; otherwise they may break when the generator set is started.
Procedure
- Disconnect the field leads from the brush block (F1, F2).
- Remove the two mounting screws.
- Withdraw the brush block from the alternator end bell.
- Inspect the brush block: if either brush is shorter than 11 mm (7/16 inch), binds, or is damaged, replace the brush block assembly.
- When installing the brush block, keep the brushes retracted with the wire through the hole; remove the wire after bolting the block in place.
- If the slip rings have grooves, pits, or other damage, use a Scotch Brite pad or commutator stone to remove light wear or corrosion.
Tools required
- Scotch Brite pad or commutator stone Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Minimum brush length: 11 mm (7/16 inch)
Full service-parts list: Cummins/Onan C20 N6 →
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.