Daikin SkyAir

Daikin SkyAir Error Code U1

Troubleshooting guide for the Daikin SkyAir system fault U1.

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What It Means

Reverse phase, open phase.

Possible Causes

  • Power supply reverse phase.
  • T phase open phase.
  • Defective outdoor unit PCB (A1P).

Not sure which one it is — or if it's none of these? Try ACLogics today.

Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis

Reverse phase, open phase

All Recorded Causes

Power supply reverse phase T phase open phase Defective outdoor unit PCB (A1P)

Verify Before Replacing Parts

  1. Confirm the exact Daikin model family and skyair context before acting on a generic code description.
  2. Start with the exact model documentation and verify the full operating sequence before replacing parts, particularly around power supply reverse phase.
  3. Use the listed causes as branches to confirm or eliminate with measurements, not assumptions — t phase open phase is a reasonable second branch.
  4. After the correction, run the system long enough to confirm the skyair fault does not return under normal load.

Diagnosing SkyAir across a fleet?

ACLogics standardizes commercial SkyAir diagnostics across your whole team — consistent steps, less guesswork on every call.

See the commercial workflow →