Generator shuts down during operation; controller shows AL05 – Overspeed Shutdown

Safety first: Keep the generator in STOP and isolate battery negative. Overspeed can cause severe mechanical damage; do not repeatedly attempt restarts until the cause is understood.

• Check speed sensor (magnetic pickup): Locate the speed sensor on the flywheel housing. Inspect the cable for chafing and the connector for corrosion. Remove the sensor and check for metal filings on the tip; clean and reinstall with the correct air gap (typically 0.5–1.0 mm, refer to engine manual).
• Inspect governor/actuator linkage: On mechanical governors, ensure the throttle linkage moves freely and returns to idle by spring force. On electronic actuators, check the actuator lever for binding.
• Verify controller speed settings: In the Deep Sea or FG Wilson controller configuration, confirm that nominal speed (e.g., 1500 or 1800 rpm) and overspeed threshold are correctly set for the alternator frequency (50/60 Hz). This usually requires technician access.
• Test without load: After checks, start in MANUAL with no load and monitor engine speed/frequency. If speed is unstable or high, stop immediately and have a qualified technician adjust the governor.