Controller displays E005 Underspeed and the generator trips off load

Safety first: Ensure the generator is isolated from the load before testing. Avoid running the unit for long periods at low frequency as it can damage connected equipment.

• Check load level: Review the automatic transfer switch (ATS) or load breakers. Confirm that the total kW and kVA do not exceed the Atlas Copco generator rating. Shed non‑essential loads and retest.
• Inspect fuel supply: Verify the main fuel tank has adequate fuel. Check for closed isolation valves, kinked hoses, or clogged pre‑filter/water separator. Replace fuel filters if service is overdue.
• Observe engine response: Start the generator in manual mode with no load. If it still runs below rated speed/frequency, suspect a governor or actuator issue.
• Check speed sensor and wiring: As with overspeed faults, inspect the magnetic pickup and harness for damage or loose connections that could cause intermittent speed readings.
• Controller calibration: Confirm the rated frequency (50/60 Hz) and speed parameters in the controller match the generator nameplate.

Persistent underspeed under normal load requires governor calibration or repair by an authorized technician.