Cummins/Onan — Adjusting the Governor (AC Sets)
Adjustments
From a Cummins/Onan service manual covering: 0.6MAJ, 1.0MAJ, 1.5MAJ, 1.5MAJ-224R, 1.5MAJ-232R, 2.5MAJ. Check it applies to your exact model before use.
Applies to: Cummins/Onan 2.5MAJ
Procedure
- Connect voltmeter across generator output.
- With no electrical load, start set and adjust speed adjusting nut to approximately 126 volts maximum for a 120-volt set.
- Apply full rated electrical load; voltage should be approximately 108 volts or higher.
- For 240-volt plants, 252 volts at no-load is maximum and 216 volts full-load is minimum.
- If voltage spread is too great, move governor speed spring end closer to governor shaft.
- Test governor action at various load conditions.
- If hunting, turn sensitivity stud slightly outward; any change requires speed readjustment.
- If using tachometer, full-load speed for 60 cycle 4-pole is 1800 rpm, 2-pole is 3600 rpm; spread not more than 100 rpm (1800) or 200 rpm (3600).
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
- 1800 rpm 4-pole FridayParts $14.13
- 3600 rpm 2-pole FridayParts $14.89
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.