Controller displays F03 – Underspeed shutdown during start or under load

Safety first: Disable automatic start and ensure the generator breaker is open before troubleshooting.

• Check fuel level and supply: Verify the day tank and main tank fuel levels. Ensure all fuel isolation valves to the MTU engine are open.
• Inspect fuel filters: Check primary and secondary fuel filters on the engine. If they are old or show signs of contamination, replace them with MTU-approved filters and prime the system.
• Governor actuator inspection: Observe the electronic actuator or throttle linkage while commanding a start. Look for sluggish movement, sticking, or no movement. Check the actuator electrical connector for corrosion or loose pins.
• Controller speed settings: In the MTU controller, verify that the rated speed (e.g., 1500/1800 rpm) is correctly configured and that droop/isochronous settings are appropriate for the application.
• Air intake and exhaust: Inspect air filters and intake ducting for blockages. Check exhaust system for restrictions that could limit engine power.
• Test under light load: After maintenance, clear the F03 alarm and run the generator at no load, then gradually apply load while monitoring frequency. If underspeed recurs, the governor or fuel injection system may require professional service.