Code 29
Onan
Low AC Output Voltage
Generator shuts down; Code 29 displayed indicating low voltage output
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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
Failed voltage regulator, Weak residual magnetism in alternator, Shorted stator winding, Incorrect engine speed (underspeed)
How to Fix / Troubleshooting
Safety first: Open the main breaker and disable auto-start. Use a true RMS voltmeter rated for the generator voltage.
- Verify engine speed: Use a tachometer to confirm engine RPM is at the specified value (e.g., 1800 or 3600 RPM depending on model). Correct any governor issues causing underspeed.
- Measure output voltage: With no load, measure line-to-line and line-to-neutral voltages at the generator terminals. If significantly low, suspect regulator or alternator issues.
- Inspect regulator connections: Check the voltage regulator harness for loose or burned connectors. Reseat and clean as needed.
- Test regulator: Follow Onan service procedures to test the regulator. If it fails tests, replace with the correct Onan part.
- Alternator check: If a new regulator does not restore voltage, the stator or rotor may be damaged and require professional replacement.
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Repair Difficulty
Professional Required
5/5
Required Part
Voltage Regulator
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