Controller shows E04 and the engine shuts down after running for a short period, especially under load.

Safety: Allow the engine to cool completely before opening the cooling system. Hot coolant can cause severe burns.

• Check coolant level: Open the radiator cap or expansion tank cap only when cool. Top up with the correct coolant mixture recommended by Himoinsa/engine manufacturer.
• Inspect radiator and airflow: Check that the radiator fins are not blocked by dust, debris, or plastic bags. Clean with low-pressure compressed air from the inside out. Ensure louvers and ventilation openings in the Himoinsa canopy are unobstructed.
• Verify fan operation: Inspect the radiator fan, fan belt tension, and condition. Replace worn or broken belts. On electric fan models, check the fan motor fuse, relay, and wiring.
• Check coolant temperature sensor: Locate the sensor on the engine. Inspect the connector and wiring. Test resistance vs. temperature according to the engine manual. Replace if out of specification.
• Bleed air from system: After topping up coolant, bleed any trapped air using bleed points on the engine or radiator to prevent hot spots.
• Test under light load: Restart the generator and apply a moderate load. Monitor temperature on the controller. If overheating persists, the water pump or thermostat may be faulty and should be checked by a technician.