Safety first: Allow the engine to cool fully before opening the cooling system. Isolate battery negative and disable AUTO mode.

Check coolant level: Open the radiator or header tank cap when cool. Top up with the correct coolant mixture. Also check the expansion bottle level if fitted.
Inspect for leaks: Look under the set and around the radiator, hoses, water pump, and engine block for dried coolant residue or wet areas.
Check coolant level sensor: Locate the level probe or float in the header tank. Disconnect the connector and inspect for corrosion. Clean contacts and reseat. If possible, test the sensor with a multimeter according to the wiring diagram.
Pressure test (advanced): If coolant loss is frequent with no visible leaks, a cooling system pressure test or engine compression test may be required; contact a qualified technician.
Test run: After topping up and fixing leaks, clear the alarm and run the generator while monitoring coolant level and temperature.

Generator shuts down; controller displays AL09 – Low Coolant Level

Possible Causes