Controller shows E05 / UNDERSPEED or UNDERFREQUENCY and the generator shuts down or will not accept load.

Safety first: Disable AUTO and open the generator output breaker. Do not allow the generator to run at low frequency under load, as it can damage connected equipment.

• Reduce load: If the fault occurs only when large loads start (e.g., central AC), stagger the startup of heavy loads or reduce total connected load. Confirm the generator kW rating matches the home load.
• Check fuel supply: Verify adequate LP/NG pressure at the generator while running. Undersized gas piping or a restricted gas regulator can cause the engine to bog down.
• Inspect air filter and spark plug: Replace a clogged air filter and worn spark plug. Restricted air or weak ignition reduces engine power.
• Check governor actuator: On models with an electronic governor actuator, inspect the linkage and wiring. Ensure the actuator moves freely and is not binding.
• Verify speed sensor: Inspect the engine speed sensor for metal shavings on the tip and correct mounting gap. Clean and reseat the connector.

If E05 persists with normal load and good fuel supply, a technician should check governor calibration and engine performance.