UNDERVOLTAGE
Guardian Generator Output Voltage Too Low

Controller displays UNDERVOLTAGE; output voltage is significantly below nominal even with light 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

Weak engine power due to fuel or ignition issues, Failing voltage regulator, Shorted stator winding, Loose main output connections

How to Fix / Troubleshooting

Safety first: Open the generator main breaker and place the controller in OFF before testing.

  • Check engine performance: Ensure the engine is running smoothly at proper speed. Replace clogged air filter, fuel filter, and worn spark plugs as needed.
  • Inspect main connections: With power off and battery disconnected, tighten all main output lugs and neutral connections in the Guardian transfer switch and generator terminal block.
  • Test no-load voltage: Start the generator with the main breaker open and measure line voltage. If still low, suspect the AVR or stator.
  • Inspect AVR: Check for burned components or melted connectors on the AVR. Replace if damaged.
  • Professional diagnosis: If UNDERVOLTAGE remains after AVR replacement, a stator winding test by a qualified technician is required.
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Repair Difficulty

Hard 4/5

Required Part

Generator Stator
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