Generator runs but controller displays E15 and AC output is lost or intermittent.

Safety first: Turn OFF the generator, disconnect battery, and ensure the unit cannot start automatically. Use caution when opening the alternator end‑bell.

• Check AVR first: Inspect the automatic voltage regulator for burnt components or odor. Verify all connectors are seated. If the AVR shows visible damage, replace it with a DuroStar‑compatible unit.
• Inspect brushes and slip rings: Remove the alternator rear cover to access the brush holder (if brush‑type). Check brush length and spring tension. Replace worn brushes and clean slip rings with fine emery cloth.
• Test rotor field: With brushes lifted, measure resistance across the rotor slip rings. Compare to service specs. An open circuit indicates a failed rotor that must be replaced.
• Check excitation wiring: Trace the small gauge wires from the AVR to the rotor/brushes and stator. Tighten loose connections and repair damaged wires.
• Reassemble and test: After repairs, reassemble the alternator, start the generator, and verify stable AC output and that E15 clears.