Generator produces power but voltage is unstable or fluctuates under load

Safety first: Open the main breaker before working inside the generator. Use a true RMS meter to monitor voltage.

• Check load behavior: Identify large motor loads cycling on and off. Stagger their operation or reduce total load to see if instability improves.
• Inspect sense wiring: Tighten and clean all small-gauge sense wires from alternator to regulator and controller.
• Brush and slip ring inspection: On brush-type units, inspect brushes for wear and ensure good contact with slip rings. Replace worn brushes and clean rings.
• Replace regulator: If wiring and brushes are good but voltage remains unstable, replace the voltage regulator with an Onan-approved part.