Cummins/Onan — Servicing the Brush Block and Slip Rings
Maintenance · generator brush block
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDKB, Cummins/Onan MDKBH
Before you start
- Disconnect the negative battery cable to prevent accidental starting.
Procedure
- Remove the enclosure front/left side assembly or swing it out to the left.
- Move the second resonator chamber out of the way.
- Disconnect the field leads from the brush block, remove the mounting screw and withdraw the brush block.
- Replace the brush block assembly if either brush is shorter than 7/16 inch (11 mm), binds or is damaged.
- Reconnect F- (black) to the outside terminal and F+ (red) to the inside terminal.
- Inspect the slip rings for grooves, pits or other damage and clean with a Scotch Brite pad or commutator stone.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Replace brush block if either brush is shorter than 7/16 inch (11 mm)
Full service-parts list: Cummins/Onan MDKB →, Cummins/Onan MDKBH →
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.