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ErrorLib — Industrial Fault Code Library

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U1-UP

Outdoor Unit Malfunction

Mitsubishi Electric · PAR-21MAA MA Remote Controller

What does U1-UP mean?

This range of codes (U1 through UP) indicates a general malfunction within the outdoor unit, as displayed on the remote controller LCD. For specific diagnostic details, further reference to the detailed error code list in the manual is required.

Common Causes

  • Malfunction of the outdoor unit's compressor control system.
  • Failure in the outdoor unit's refrigerant flow control valve.
  • Abnormal sensor readings from the outdoor unit (e.g., temperature, pressure).
  • Loss of communication signal from the outdoor unit's main controller.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Refer to the 'Error code list' in section 'V.4.2.Error code list' of the complete manual for specific diagnostic information related to U1-UP codes.

  2. 2

    Visually inspect the outdoor unit for any signs of damage, loose electrical connections, or abnormal sounds during operation.

Browse all codes in this manual (26)
Verified technical data. Last updated: April 2026

Related Faults

----No Error History00Communication Error (Indoor/Outdoor/Remote Controller)A0~A8M-NET System Communication Error
Source: Mitsubishi Electric PAR-21MAA MA Remote Controller
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