General Assist Technical Reference
E: 39 – Indoor Unit Power Supply Error for Fan Motor
Indoor unit troubleshooting guide
Source service manual: SR_MU006EF_06 • Revision 06 • Issue date 7 March 2025
Quick answer: Error E:39 is an indoor-unit fan motor power-supply error detected by the indoor unit main PCB. The service manual identifies three main cause groups: an external cause, a connector connection failure, or an indoor main PCB failure.
Electrical safety: Isolate the air conditioner before disconnecting or reseating any fan motor or PCB connectors. Live-voltage testing must only be carried out by appropriately qualified personnel using the applicable service manual and safe electrical work practices.
1. Error indication
| Indicator | Display |
|---|---|
| Operation indicator | 3 flashes |
| Timer indicator | 9 flashes |
| Economy indicator | Continuous flashing |
| Error code | E: 39 |
2. Detection condition
The source service information identifies the indoor unit main PCB as the detecting actuator. The error can be detected in the following situations:
- A momentary power cut-off occurs.
- The fan motor does not start.
3. Forecast causes
| Cause group | What to investigate |
|---|---|
| External cause | Check whether the error followed a momentary interruption or instability of the power supply. |
| Connector connection failure | Inspect the fan motor and indoor PCB connector connections for poor seating, damaged terminals or an interrupted connection. |
| Main PCB failure | If external causes and connector connections are eliminated, the indoor main PCB remains a listed fault cause. |
4. Recommended diagnostic sequence
- Confirm the fault. Verify E:39 or the corresponding 3 / 9 / continuous-flash indicator pattern.
- Check for an external power event. Determine whether there has been a momentary power interruption or other supply event immediately before the fault.
- Isolate power. Switch the system off and follow the required electrical isolation procedure before accessing the indoor electrical section.
- Inspect connector connections. Check the fan-motor-to-PCB connection and associated plugs/terminals for loose, partially inserted or damaged connections.
- Restore power and retest. After correcting any connection issue, restart the system and confirm whether the indoor fan starts and the error returns.
- Assess the indoor main PCB. If the external cause and connector connection have been ruled out and E:39 remains, the service manual lists main PCB failure as a forecast cause. Continue with the model-specific PCB checks in the applicable service manual before replacement.
Important distinction: E:39 is described as a power supply error for the fan motor. It should not automatically be treated as confirmation that the fan motor itself has failed. Follow the listed cause sequence and verify the circuit before replacing components.
5. Service outcome guide
| Finding | Action |
|---|---|
| Fault follows a momentary power interruption and does not return after restart | Confirm normal operation. No component fault is established by the source information. |
| Loose or poor connector connection found | Correct the connection and retest operation. |
| External cause and connector issue ruled out; E:39 remains | Proceed with model-specific indoor main PCB diagnosis. Main PCB failure is a listed cause. |
Source basis: Fujitsu General service manual SR_MU006EF_06, Revision 06, issued 7 March 2025 – E:39 Indoor unit power supply error for fan motor (Indoor unit). This article preserves the source fault indicators, detecting actuator and listed forecast causes. Diagnostic wording is arranged into a Freshdesk-friendly service sequence without adding unsupported test voltages or component specifications.