E4
Fujitsu
Outdoor Unit EEPROM or Control Fault
Outdoor unit does not start compressor, E4 error displayed on indoor unit
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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
Corrupted outdoor PCB EEPROM, Failed outdoor main PCB, Power surge or lightning damage, Loose control connectors on outdoor PCB
How to Fix / Troubleshooting
Safety first: Turn off the outdoor disconnect and verify no voltage is present before opening the outdoor unit's electrical panel.
- Power reset: Turn off both indoor and outdoor power for at least 5–10 minutes to fully discharge capacitors. Restore power and test operation.
- Inspect outdoor PCB: Remove the outdoor control box cover. Check for burnt components, insect nests, moisture, or corrosion on the PCB and connectors.
- Reseat connectors: Gently unplug and replug low-voltage connectors on the outdoor PCB, especially those leading to any daughter boards or EEPROM modules.
- Check for water ingress: If the control box shows signs of water entry, dry the area thoroughly and correct any missing grommets or seals. However, water-damaged boards usually must be replaced.
- Board replacement: If E4 persists and there is no wiring error, the outdoor main PCB (with EEPROM) typically needs replacement. This should be done by a Fujitsu-trained technician to ensure correct part selection and firmware.
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Repair Difficulty
Professional Required
5/5
Required Part
Outdoor Main PCB (Inverter Control Board)
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