Daikin aircon U3 error code
Use this Daikin U3 error code guide to confirm the source table meaning, capture the reporting equipment and model, and match the service manual before diagnosis. Match the model first; same-looking codes can point to different rows.
What does Daikin U3 mean?
Daikin U3 is listed as check operation not executed or transmission error, check operation not executed, and system test run not yet executed, so system operation is not possible in mixed model-family source rows, including VRV X RXQ-A(N)R cooling only, VRV IV+ REYQ / REMQ heat recovery, VRV 5-S RXYSA R32, VRV 5 Heat Recovery REMA / REYA R32, VRV 5 Heat Pump RYMA / RXYA R32, and ERA-AYF AHU / air curtain. The loaded row is source-backed by official diagnostic material. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.
Choose the matching source row
The same visible code has more than one source-backed meaning. Match the model family, system type, or reporting unit before approving parts.
| Code | What it means | What to check first |
|---|---|---|
| Fan Coil | Check operation not executed or transmission error | Match this row to the installed model or reporting unit, then use the source-specific checks below. |
| VRV X RXQ-A(N)R cooling only | Check operation not executed | Match this row to the installed model or reporting unit, then use the source-specific checks below. |
| U3-03 - system | System test run not yet executed, so system operation is not possible | Execute the system test run. Match the alternating U3-03 display to the system source row. |
| U3-04 - system | An error occurred during the test run | Re-execute the test run. Match the alternating U3-04 display to the system source row. |
| U3-05 - system / U3-06 - system | Test run aborted | Re-execute the test run. Match the alternating U3-05 display to the system source row. |
| U3-07 - system / U3-08 - system | Test run aborted because of communication issues | Check the communication wiring and re-execute the test run. Match the alternating U3-07 display to the system source row. |
| VRV 5-S R32 - U3 / VRV 5 Heat Recovery R32 - U3 / VRV 5 Heat Pump R32 - U3 | System test run has not been executed | Complete the prescribed system test run before normal operation. |
| ERA-AYF AHU / air curtain | Test run not completed or aborted (U3-03/04/05/06/07/08) | Match this row to the installed model or reporting unit, then use the source-specific checks below. |
What to do now
Use these steps to record evidence and match the installed model to its service manual before diagnosis or a repair quote.
Record U3 and match the service manual
Record U3 and stop there; the source table gives no customer reset procedure. Arrange diagnosis with the matching service manual.
No manufacturer reset steps listed for U3
Capture the complete U3 error code and model stickers first. The source table lists the meaning but no customer reset procedure; do not treat a generic power-cycle as manufacturer guidance.
Send these to us
U3 error code, a clear display photo, Daikin indoor and outdoor model stickers, the controller, gateway, or unit that reported the code, operating mode and affected area, and any power or setting changes made after the code appeared
Source-specific guidance
These diagnostic-reference notes help match the code to the exact model. Electrical, refrigerant, wiring, resistance, and component checks are technician work, not DIY steps.
| Source detail | What it says |
|---|---|
| Singapore / model note | Official Daikin SM-TS3 self-diagnosis row. Manual causes: Check operation is not executed. |
| Singapore / model note | Official Daikin RXQ6-48A(N)R cooling-only service-manual row. Confirm the installed model and matching regional manual before diagnosis; this source is not claimed as universal across every Daikin VRV generation. |
| Singapore / model note | Official Daikin 4PEN561154-1C overview row for REYQ8~20 and REMQ5U7Y1B VRV IV+ heat-recovery systems. The guide refers technicians to the service manual for the complete code list and detailed troubleshooting. |
What to check before repair
The source table establishes the code meaning, not a repair procedure. Capture evidence first; model-specific tests belong to the matching service manual.
| You can check | Technician should confirm |
|---|---|
| Photograph the complete U3 error code before taking any action. | Confirm U3 exactly and record which controller, gateway, or unit reported it. |
| Capture the Daikin indoor and outdoor model stickers and identify which controller or unit reported it. | Match the indoor and outdoor model stickers, installed family, and reporting equipment to the source scope. |
| The source table provides no customer reset procedure. Preserve the evidence and use the matching service manual for any system action. | Follow the matching service-manual procedure and keep measured test evidence before naming a failed part. |
Source-bounded repair decision
Daikin U3 confirms the source-table fault label, not a failed part or repair procedure. Match the installed model to its service manual and require measured diagnostic evidence before approving parts, settings, or refrigerant work.
Whether the reporting controller or unit and exact installed model are confirmed.
What the matching service-manual procedure and measured tests show.
Whether the proposed repair names the evidence for the failed part or condition.
Daikin U3 questions
What does the Daikin U3 error mean?
Can I fix a Daikin U3 error myself?
Is it safe to keep running the aircon with a U3 error?
What causes a Daikin U3 error?
Will a Daikin U3 error need a repair or a full replacement?
What should I send a technician about a Daikin U3 error?
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Use this quote-check guide only after the matching service manual identifies the diagnostic path.