P1
Mitsubishi Electric
Inverter DC Bus Overvoltage / Undervoltage
Outdoor unit stops, P1 error logged or displayed, compressor does not run
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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
Unstable power supply, Loose power terminals at outdoor unit, Failed inverter PCB DC bus capacitors, Incorrect supply voltage (phase or rating mismatch)
How to Fix / Troubleshooting
Safety first: This involves high voltage DC. Only qualified personnel should open the outdoor control box. Always isolate power at the main disconnect.
Steps:
- Check supply voltage: Verify that the mains voltage and phase match the unit’s nameplate. Large deviations can trigger P1.
- Inspect terminals: Tighten all power input terminals and check for discoloration or heat damage.
- Power quality: If voltage is unstable, consider installing a voltage stabilizer or consult the power utility.
- PCB inspection: Look for bulged or leaking DC bus capacitors on the inverter PCB. If present, the PCB must be replaced.
- Technician service: Detailed DC bus and inverter diagnostics should be performed by a Mitsubishi Electric-trained technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Outdoor Inverter PCB
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