JCB
Loss of Excitation / No Output
Generator runs but produces no AC voltage at the terminals, with no specific code on basic controllers.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed AVR, Loss of residual magnetism, Open circuit in rotor winding, Broken excitation wiring
How to Fix / Troubleshooting
Safety: Confirm the generator is isolated from all loads and mains before testing.
- Measure terminal voltage: Verify zero or very low voltage at the alternator output with a multimeter.
- Inspect AVR and wiring: Open the alternator terminal box on the JCB set. Check AVR connections and look for burnt components or loose wires.
- Field flashing (qualified personnel): If residual magnetism is lost, briefly apply a low‑voltage DC source across the field winding as per manufacturer instructions to restore magnetism.
- Rotor continuity: Test rotor field winding resistance via slip rings (if fitted). An open circuit indicates rotor failure requiring alternator repair.
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Repair Difficulty
Professional Required
5/5
Required Part
Alternator Rotor Assembly
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