System Diagnosis
Reverse phase, open phase
Daikin Packaged
Error Code U1
Troubleshooting guide for the Daikin Packaged system fault U1.
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.
Potential Causes & Solutions
- Power supply reverse phase.
- T phase open phase.
- Defective outdoor unit PCB (A1P).
Verify Before Replacing Parts
- Confirm the exact Daikin model family and packaged context before acting on a generic code description.
- Start with the exact model documentation and verify the full operating sequence before replacing parts.
- Use the listed causes as branches to confirm or eliminate with measurements, not assumptions.
- After the correction, run the system long enough to confirm the code does not return under normal load.
Field Signals to Confirm
What usually confirms it
A consistent failure pattern that matches the code and can be tied to a measured condition.
What can fool you
Generic code text without model context can send you after the wrong component.
When to Escalate the Call
- The code behavior does not match the published description for the exact model.
- You have conflicting evidence across multiple branches and need model-specific escalation.
Still unsure about this fault?
ACLogics walks you through Daikin Packaged diagnostics step-by-step — so you confirm the cause before swapping parts.
