Cummins/Onan — Electric Governor Calibration Checks
Adjustments
From a Cummins/Onan service manual covering: 4BT3.9-GC1, 4BT3.9-GC2, 6BT5.9-GC1, 6BT5.9-GC2, 6CT8.3-GS/GC1, 6CTA8.3-GS/GC1, 6CTA8.3-GS/GC2. Check it applies to your exact model before use.
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Procedure
- Start generator set.
- Adjust no-load speed to desired allowable speed droop.
- Warm up and adjust Speed potentiometer to desired frequency or r/min.
- With no load, turn GAIN clockwise until actuator lever oscillates.
- Reduce GAIN counterclockwise until lever stable; upset lever; 3 diminishing oscillations acceptable.
- Reduce GAIN one division; turn I fully clockwise; adjust I until lever stable.
- Apply and remove loads to check response.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Isochronous 60.0 Hz/1800 r/min
- 3% droop 61.8 Hz/1854 r/min
- 5% droop 63.0 Hz/1890 r/min
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.