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ErrorLib — Industrial Fault Code Library

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Ud (100)

Overheat Protection (Outdoor Pipe)

Mitsubishi Electric · PUZ-HA30/36NHA4 Outdoor Unit

What does Ud (100) mean?

The outdoor pipe thermistor (TH2) detects a temperature of 70°C [158°F] or more during compressor operation. This indicates either a defective outdoor fan (fan motor), a short cycle of the outdoor unit during cooling operation, or a faulty outdoor pipe thermistor (TH2).

Common Causes

  • Outdoor pipe temperature has exceeded the overheat protection threshold (Ud code).
  • Insufficient refrigerant flow causing localized overheating.
  • Blockage in the outdoor unit's heat exchanger or piping.
  • Ambient temperature is too high, leading to poor heat dissipation.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the outdoor unit air passage for obstructions.

  2. 2

    Turn the power off and on again to clear the error code. If U9 is subsequently displayed, follow the U9 troubleshooting procedures.

Browse all codes in this manual (45)
Verified technical data. Last updated: April 2026

Related Faults

01Overvoltage Error02Undervoltage Error04L1 or L2-Phase Open Error
Source: Mitsubishi Electric PUZ-HA30/36NHA4 Outdoor Unit
Open Manual (Page 28)Search more codes in this manual