PHASE LOSS
Guardian
Loss of One or More Output Phases
On three-phase Guardian units, controller displays PHASE LOSS or PHASE FAILURE; generator may shut down or lock out.
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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
Open stator winding on one phase, Loose phase conductor at terminal block, Faulty phase-sensing circuit on control board, Blown line fuse (if used)
How to Fix / Troubleshooting
Safety first: Open the generator main breaker and lock it out. Place the controller in OFF. Three-phase faults can damage motors quickly.
- Inspect terminal block: Check all phase conductors (L1, L2, L3) at the generator output terminal block for tightness and discoloration.
- Check downstream connections: Inspect wiring between the generator and transfer switch for loose or burned connections.
- Measure phase voltages: With the main breaker open, start the generator and measure voltage between each phase and neutral, and phase-to-phase. A missing phase indicates stator or internal connection failure.
- Control board sensing: If all voltages are present but PHASE LOSS persists, the phase-sensing circuit on the control board may be defective.
- Professional repair: Stator or control board replacement should be performed by a qualified Guardian technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Three-Phase Stator Assembly
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