Generator shuts down and controller shows F05 Overspeed; engine revs unusually high just before shutdown.

Safety first: Overspeed conditions are dangerous and can cause catastrophic engine failure. Do not repeatedly restart the generator until the cause is identified. Set the controller to OFF and disable auto-start.

• Inspect throttle and governor linkage: With the engine off, manually move the throttle lever and governor linkage. Ensure they move smoothly and return to idle without binding. Lubricate pivot points lightly if stiff and remove any debris obstructing movement.
• Check speed sensor: Locate the magnetic pickup or Hall-effect speed sensor near the flywheel or ring gear. Inspect the sensor tip for metal shavings and clean gently. Verify the sensor is mounted at the correct gap specified by Siemens (often 0.5–1.0 mm). Tighten the locknut.
• Inspect wiring to governor module: Follow the harness from the speed sensor and governor actuator to the controller or separate governor module. Look for chafed insulation, loose connectors, or corrosion. Repair or replace damaged wiring.
• Controller settings: If recent service was performed, verify that rated speed (e.g., 1500 or 1800 RPM) and overspeed thresholds are correctly programmed in the Siemens controller according to the model manual. Incorrect settings can cause nuisance F05 trips.
• Professional calibration: If overspeed persists, the electronic governor module or actuator may be faulty. A qualified technician should perform RPM calibration and replace the governor actuator if necessary.