H4
Friedrich Inverter Module / IPM Overheat or Overcurrent (inverter models)

Display shows H4, unit may shut down heating or cooling

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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

Blocked airflow causing high load, failing inverter power module, poor heat sinking of outdoor PCB, incorrect supply voltage, shorted compressor

How to Fix / Troubleshooting

Safety: Disconnect power before accessing the outdoor inverter board. High DC voltages may be present.

Steps:

  • Improve airflow and load: Clean indoor and outdoor coils and filters to reduce system load.
  • Check outdoor PCB cooling: Ensure the inverter board heat sink is not clogged with dirt and that any cooling fan (if equipped) is operating.
  • Inspect for damage: Look for burnt components or discoloration on the inverter board. If present, the board must be replaced.
  • Compressor check: A shorted compressor can cause H4. A technician should test compressor windings before replacing the board.

Warning: Inverter board diagnosis and replacement should be performed by a qualified technician due to high-voltage DC circuits.

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Repair Difficulty

Professional Required 5/5

Required Part

Outdoor Inverter PCB
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