Generator stops and displays E003 High Engine Temperature on the Atlas Copco controller

Safety first: Allow the engine to cool completely before opening the radiator cap or coolant reservoir. Hot coolant under pressure can cause severe burns. Isolate the battery before working near the fan or belts.

• Check coolant level: Inspect the expansion tank and radiator (when cool). Top up with the correct coolant mixture recommended for your Atlas Copco generator engine. Investigate any rapid loss of coolant.
• Inspect radiator and airflow: Remove debris, dust, or plastic bags from the radiator fins and air intake grilles. Clean with low‑pressure compressed air from the engine side outwards.
• Check fan and belt: Verify the radiator fan turns freely and the drive belt has proper tension and is not cracked or glazed. Replace worn belts and tension according to the engine manual.
• Verify coolant temperature switch/sensor: Locate the high temp switch or sensor on the thermostat housing or cylinder head. Inspect wiring and connectors for corrosion. If the engine is not actually overheating (normal temp on mechanical gauge), test or replace the sensor.
• Bleed air from system: After coolant service, bleed air from bleed screws or high points to prevent air locks that cause localized overheating.

If E003 recurs despite correct coolant level and clean radiator, a failing water pump or head gasket may be the cause and requires professional diagnosis.