AL18
SDMO
Frequency Out of Limits
Controller shows AL18 indicating frequency out of range; generator will not connect to load.
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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
Incorrect governor speed setting, Faulty engine speed sensor, Unstable electronic governor module, Sudden large load changes on SDMO generator
How to Fix / Troubleshooting
Safety first: Isolate the generator from load before adjusting speed or governor settings.
- Check no-load frequency: Start the generator and measure frequency with a calibrated meter. Adjust the governor speed setting to achieve nominal frequency (50 or 60 Hz) as specified.
- Inspect speed sensor: Verify the magnetic pickup or speed sensor is secure and clean. Replace if the signal is intermittent or noisy.
- Test governor module: Observe engine response to small load changes. If frequency swings widely, the SDMO governor module may require tuning or replacement.
- Stabilize load application: Avoid instant application of large motor loads. Use soft starters or staggered starting where possible.
- Reset AL18: After stabilizing frequency, clear the alarm and test under typical load conditions.
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Repair Difficulty
Hard
4/5
Required Part
Electronic Governor Module
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