Generator shuts down with AL05, indicating underspeed; the engine runs rough and cannot reach rated frequency.

Safety first: Place the generator in OFF, isolate the load, and allow the engine to cool before servicing fuel or air systems.

• Inspect and replace fuel filters: Check the SDMO primary and secondary fuel filters for contamination. Replace them if dirty or waterlogged. Bleed the fuel system after replacement.
• Check for fuel line restrictions: Inspect flexible hoses and rigid lines for kinks, collapsed sections, or partially closed valves. Ensure that the SDMO fuel transfer pump (if fitted) is operating correctly.
• Clean or replace air filter: Remove the air filter element and inspect it. If heavily soiled, replace it with the correct SDMO-specified element. Do not run without a filter except briefly for testing.
• Verify governor linkage: On mechanical governors, ensure that linkages move freely and that return springs are intact. On electronic governors, check the actuator for full travel and recalibrate if required per the SDMO/engine manual.
• Load test: After clearing AL05, start the generator and gradually apply load while monitoring the frequency. Avoid sudden full-load application on a cold engine.