Cummins/Onan — Verify Overspeed Fault Detection
Testing & diagnosis · Governor / overspeed control
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan GGHE, Cummins/Onan GGHF, Cummins/Onan GGHG, Cummins/Onan GGHH
Procedure
- For Type A sets, move the throttle lever/linkage to increase RPM to the overspeed shutdown range.
- For Type B sets, remove the two screws securing the throttle body cover and remove cover.
- Use special tool P/N 420-0604 to turn the end of the throttle shaft.
- With genset operating at no load, slowly rotate the shaft clockwise until RPM reaches the overspeed limit and shuts down.
- Replace the throttle body cover after completing the test.
Tools required
- special tool P/N 420-0604 Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Type A overspeed shutdown: 2250 ± 30 RPM
- Type B overspeed shutdown: 2400 ± 30 RPM
Full service-parts list: Cummins/Onan GGHE →, Cummins/Onan GGHF →, Cummins/Onan GGHG →, Cummins/Onan GGHH →
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.