SYNC LOSS
Guardian
Loss of Synchronization Between Generator and Utility
On units with advanced controllers, SYNC LOSS or OUT OF SYNC alarm appears when transferring load.
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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
Incorrect frequency or voltage, Faulty sync sensing circuit, Misconfigured controller settings, Loose sensing leads to controller
How to Fix / Troubleshooting
Safety first: Do not attempt to manually force transfer when a sync alarm is active. Leave the main breaker open and controller in OFF.
- Verify generator frequency and voltage: Start the generator with no load and measure output. Correct UNDERFREQUENCY or OVERVOLTAGE issues first.
- Inspect sensing leads: Check the low-voltage sensing wires from the generator and utility to the Guardian controller for tight connections and damage.
- Controller configuration: Confirm that the controller is programmed for the correct system voltage and phase configuration.
- Professional calibration: If SYNC LOSS persists, a Guardian technician must test the sync sensing circuit and controller firmware.
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Repair Difficulty
Professional Required
5/5
Required Part
Control Board (Sync Sensing Circuit)
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