Generator runs but controller displays UNDERSPEED or LOW ENGINE SPEED alarm and may shut down under load.

Safety first: Place the generator in OFF mode, disconnect battery negative, and isolate from load (open output breaker) before troubleshooting.

Steps:

• Check for overload: Ensure the main output breaker on the Gillette generator is not feeding more load than the unit’s rated kW. Underspeed often occurs when the generator is overloaded. Shed non-essential loads and retest.
• Fuel system: Replace the fuel filter(s) and inspect fuel lines for restrictions or collapsed hoses. Verify adequate fuel supply and correct gas pressure for LP/NG units.
• Governor system: Inspect the mechanical governor linkage for binding or misadjustment. On electronic systems, check the actuator and wiring. A sluggish actuator can cause low speed.
• Air intake and exhaust: Check the air filter and muffler for blockage. Replace a clogged air filter and ensure exhaust outlet is not obstructed.
• Test: Reconnect battery, start the generator with no load, and verify frequency (should be near 60 Hz). Gradually apply load and observe if speed holds. Persistent underspeed requires professional adjustment of governor settings.