Cummins/Onan — Governor Adjustment (AC Plant)
Adjustments
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Connect voltmeter across generator output.
- Start plant with no electrical load.
- Adjust speed adjusting nut for approximately 126 V maximum for 120 V plant.
- Apply full rated load and observe approximately 108 V minimum.
- For 240 V plants, 252 V maximum and 216 V minimum.
- Adjust sensitivity for closest regulation without hunting.
- If voltage spread too great, move speed spring closer to governor shaft.
- Any sensitivity change requires speed readjustment.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 126 V max no load 120V
- 108 V min full load 120V
- 252 V max no load 240V
- 216 V min full load 240V
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.