Controller displays E09 and shuts down the generator under load.

Safety first: Disconnect the building load via the transfer switch. Turn OFF the generator main breaker before testing.

• Check engine speed: Use a frequency meter to confirm the generator is running at the correct frequency (50/60 Hz). If low, address engine/governor issues first.
• Inspect load: Reduce or stagger large motor loads. Start the generator with minimal load and gradually add circuits while monitoring the voltage.
• Inspect wiring: Tighten all stator output leads at the terminal block and AVR connections. Look for heat discoloration indicating poor contact.
• Test AVR: With the engine at correct speed and low load, measure the voltage. If it remains low (e.g., <200 V on a 230 V system), the AVR may be defective and should be replaced.
• Check for winding damage: If the voltage is unstable or one phase is significantly lower, the alternator stator or rotor may be damaged; this requires professional testing.
• Clear E09: After repairs, reset the controller and verify stable voltage under normal load.