Controller displays AL04 indicating overspeed; generator stops abruptly during or shortly after start.

Safety first: Keep the generator in OFF mode and isolate load. Do not attempt to run the engine if overspeed is suspected, as it can cause severe mechanical damage.

• Inspect speed sensor: Locate the magnetic pickup sensor near the flywheel ring gear. Check for metal debris on the sensor tip and clean it carefully. Ensure the air gap between sensor and flywheel is set per engine/SDMO specification.
• Check wiring harness: Follow the speed sensor cable to the SDMO control module. Look for cuts, abrasions, loose connectors, or corrosion. Repair or replace damaged sections.
• Verify governor actuator: Observe the electronic actuator (if fitted) while attempting a start in MANUAL with fuel disabled. Ensure it moves smoothly and returns to idle position. Replace the actuator if it is sticking or unresponsive.
• Review governor settings: On sets with adjustable electronic governors, confirm that rated speed (e.g., 1500 or 1800 rpm) is correctly configured. Incorrect settings can cause overspeed trips.
• Reset alarm and test: After corrections, clear AL04 and perform a controlled start while monitoring engine speed on the SDMO display.