P4
Hitachi
Indoor–Outdoor Capacity Mismatch / Configuration Error
Unit stops with P4, sometimes immediately after start
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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
Incorrect indoor or outdoor unit combination, Wrong PCB or firmware installed, Incorrect DIP switch or jumper settings on PCB, EEPROM configuration error
How to Fix / Troubleshooting
Safety first: Turn OFF power before inspecting PCBs.
Steps:
- Verify model match: Confirm that the indoor and outdoor units are a compatible pair as per Hitachi documentation.
- Check PCB part numbers: If a PCB was recently replaced, ensure it is the correct part number for your exact model.
- Inspect configuration switches: Some models have DIP switches or jumpers for capacity or mode settings. Verify they match the service manual.
If unsure: Contact Hitachi service with full model and serial numbers to verify correct configuration.
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Repair Difficulty
Hard
4/5
Required Part
Indoor/Outdoor Main Control PCB
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