P0
Fraser-Johnston Inverter Module / DC Bus Voltage Fault

P0 code, inverter-driven outdoor unit will not start or runs at limited capacity

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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

Failed inverter power module, Incorrect line voltage, Loose DC bus connections, Shorted compressor or fan motor on inverter output

How to Fix / Troubleshooting

Safety: Inverter systems contain high DC voltages even after power is removed. Only trained personnel should service inverter modules.

  • Power down and wait: Turn off the outdoor disconnect and wait at least 10 minutes for DC bus capacitors to discharge.
  • Inspect wiring: Check all power and ground connections on the inverter board for tightness and signs of overheating.
  • Verify line voltage: Confirm supply voltage is within the specified range for the Fraser‑Johnston inverter unit.
  • Check for shorts: A technician should test compressor and fan motor windings for shorts to ground.
  • Replace inverter module: If wiring and loads test good, the inverter module may need replacement as a complete assembly.
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Repair Difficulty

Professional Required 5/5

Required Part

Inverter Power Module
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