Perkins
No AC Output / Loss of Excitation
Generator runs but produces no AC output voltage at terminals
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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, Open circuit in alternator field winding, Tripped alternator circuit breaker, Broken stator leads in terminal box
How to Fix / Troubleshooting
Safety: Confirm the generator is isolated from the ATS and load before opening the terminal box.
- Check main breaker: Ensure the generator output breaker is closed and not tripped.
- Measure voltage: Use a meter at the alternator terminals. If zero or very low, suspect excitation issues.
- Inspect AVR and wiring: Check AVR connections and look for burnt components. Verify excitation supply fuses.
- Field and stator continuity: With power off, measure resistance of field and stator windings per alternator manual. Open circuits indicate internal alternator faults.
- Replace AVR or alternator: Fit a new AVR if it has failed. Serious winding faults require alternator repair or replacement.
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Repair Difficulty
Professional Required
5/5
Required Part
Automatic Voltage Regulator (AVR)
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