Cummins/Onan — Adjusting Governor (Mechanical, HGJAB and HGJAE)
Adjustments · Mechanical governor
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HGJAA, Cummins/Onan HGJAB, Cummins/Onan HGJAD, Cummins/Onan HGJAE
Before you start
- Disconnect all voltage/frequency-sensitive devices before making carburetor/governor adjustments.
Procedure
- Warm up generator set for at least 5 minutes at 1/2 to 3/4 rated load.
- Adjust frequency with the speed adjusting nut toward the Table 11 value.
- With engine warm, remove all loads; adjust idle stop screw to 51-53 Hz (60 Hz) or 41-43 Hz (50 Hz).
- Let throttle lever go.
- Recheck and re-adjust no-load frequency per Table 11.
- Bump governor arm to see frequency stabilizes.
- Connect a rated load.
- If droop is greater than specified, move governor spring hook one or two notches toward governor shaft; recheck.
- If droop is less or set hunts, move spring hook one or two notches away from governor shaft.
Tools required
- Variable load bank up to 7 kW Amazon
- Frequency meter (within 0.3%) Amazon
- Voltmeter (within 0.5%) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Idle 51 to 53 Hz (60 Hz) or 41 to 43 Hz (50 Hz)
Full service-parts list: Cummins/Onan HGJAA →, Cummins/Onan HGJAB →, Cummins/Onan HGJAD →
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.