H99
Fisher & Paykel Inverter Overcurrent / Overvoltage Fault

Microwave displays H99 and shuts down or refuses to start a heating cycle.

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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

Intermittent short in magnetron, Inverter board sensing overcurrent, Poor grounding or loose chassis connections, Defective control board inverter control circuit

How to Fix / Troubleshooting

Safety first: Unplug the microwave. High-voltage components are dangerous.

  • Check installation and grounding: Ensure the microwave is plugged into a properly grounded outlet. Do not use adapters that defeat the ground pin.
  • Inspect chassis ground: With power disconnected, verify that the ground wire from the power cord is securely fastened to the chassis and that there is no corrosion.
  • Ventilation check: Confirm that vents are not blocked and that the cooling fan runs when the unit is operating. Overheating can cause inverter overcurrent faults.
  • Professional service: If H99 persists, the inverter or magnetron is likely faulty. These parts should be tested and replaced by a qualified Fisher & Paykel technician.
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Repair Difficulty

Professional Required 5/5

Required Part

Inverter Board
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