Fault Code E04 – Fujitsu Series 9

Meaning: Operating temperature exceeded safe limits; output may be reduced or the system may shut down.

Common causes

• Loose or damaged wiring/connector
• Connector corrosion, moisture intrusion, or contamination
• Out-of-range operating conditions
• Component wear or intermittent failure
• Improper installation or setup
• Communication wiring mismatch
• Voltage drop during compressor start

What to check first

1. Power down the unit before inspection and allow it to cool (if hot)
2. Turn power off at the disconnect before inspecting indoor/outdoor communication wiring
3. Verify connectors are seated and wiring is intact (no pinches/cuts/burn marks)
4. Confirm supply power is within specification for your unit
5. Remove debris and ensure proper ventilation/airflow
6. After correcting the suspected cause, power-cycle and retest
7. Check for terminal corrosion and tighten connections to manufacturer torque guidance

Is it safe to keep running?

Maybe. Reduce load/stop the cycle if symptoms persist, then troubleshoot to prevent damage.

Reset guidance

After correcting the underlying issue, clear the fault by power-cycling the unit, then retest during normal operation. If the code returns, stop and escalate to service diagnostics.

When to call service

• The code returns immediately after basic checks
• There are visible signs of damage, overheating, or burning odor
• The code repeats multiple times in a week
• Performance is degraded even after cleaning/ventilation checks

General reference only. Not affiliated with manufacturers. Meanings describe common patterns and may vary by exact model/version—always confirm with your model’s service manual.