Cummins/Onan — Voltage Regulator VR21 Replacement
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDKC, Cummins/Onan MDKD, Cummins/Onan RGA-OP'
Procedure
- Stop the generator set and disconnect starting battery leads, negative (-) first.
- Disconnect and label wires from the voltage regulator; refer to AC control wiring diagram.
- Remove mounting screws from old voltage regulator; install new regulator.
- Reconnect wires removed to the proper terminals.
- Set voltage as outlined in Voltage Adjustment.
Full service-parts list: Cummins/Onan MDKC →, Cummins/Onan MDKD →, Cummins/Onan RGA-OP' →
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.