Controller shows AL09 / Low Coolant Level and prevents automatic start
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Allow the engine to cool completely before opening the cooling system. Set controller to OFF and disconnect battery negative.
- Check coolant level: Remove the radiator cap or inspect the expansion tank on the Kohler-SDMO set. Top up with the specified coolant mix to the correct mark.
- Inspect for leaks: Examine radiator core, hoses, water pump weep hole, and engine block connections for dried coolant stains or wet spots. Tighten clamps and replace damaged hoses.
- Check coolant level sensor: Locate the level sensor on the radiator or header tank. Inspect wiring and connector. Clean the sensor and reseat the connector. Replace the sensor if the alarm persists with correct coolant level.
- Bleed air: If the system was very low, bleed air from bleed screws or high points per engine manual to prevent air locks.
- Reset alarm: Reconnect battery, clear AL09, and run the generator while monitoring for leaks.
Repeated low coolant alarms indicate an unresolved leak or overheating problem that should be investigated further.
Repair Difficulty
Required Part
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