Code 31
Onan
High Frequency / Overspeed Fault
Generator shuts down; Code 31 displayed indicating overspeed or frequency too high
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Misadjusted governor settings, Sticking throttle linkage, Faulty speed sensor, Defective controller speed circuit
How to Fix / Troubleshooting
Safety first: Overspeed can be dangerous. Disable auto-start and open the main breaker. Do not adjust governor without referencing the service manual.
- Inspect linkage: Check for free movement of throttle and governor linkage. Remove any obstructions and lubricate pivot points.
- Check speed sensor: Inspect the magnetic pickup for proper mounting and clean the tip. Ensure the gap is within specification.
- Verify frequency: Use a frequency meter to measure output Hz. If frequency is high with normal throttle position, the governor may be misadjusted and should be calibrated per Onan procedure.
- Controller replacement: If mechanical and sensor components are correct but Code 31 persists, the controller may require replacement by a technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Governor Linkage Assembly
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