Cummins/Onan — Adjusting PMG Excited Generator Voltage Using Voltage Regulator Trimmer
Adjustments
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDDC, John Deere 4045TFM engine, John Deere 6068TFM engine
Procedure
- If the generator set has a sound shield enclosure, remove the front access panel below the control box.
- Remove the voltage regulator access cover.
- Push the SINGLE (PARALLEL) operation switch up to SINGLE.
- Start the generator set and let voltage and frequency stabilize; disconnect all loads.
- Using a small flat-bladed screwdriver, turn the voltage trimmer clockwise to increase voltage or counterclockwise to decrease voltage.
Tools required
- Small flat-bladed screwdriver Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan MDDC →, John Deere 4045TFM engine →
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.