Controller shows GEN UNDERVOLT or LOW AC VOLTAGE; loads may drop out or transfer switch may not transfer.

Safety first: Isolate the generator from the load by opening the main breaker. Turn OFF the unit and disconnect battery negative before internal inspection.

Steps:

• Check engine speed: Start the generator and verify frequency with a meter. If frequency is low, address underspeed/governor issues first, as low speed directly reduces voltage.
• Inspect alternator connections: With power off, open the alternator terminal box on the Gillette generator. Tighten all stator and excitation winding connections and inspect for heat damage.
• AVR check: Confirm that the AVR connections are tight and that any voltage adjustment potentiometer has not been misadjusted. Slightly adjust within manufacturer limits to see if voltage responds.
• Test excitation: If there is no or very low voltage, the excitation circuit or AVR may have failed. Replacement of the AVR or alternator field components may be required.