Ud

Overheat protection (Outdoor pipe thermistor)

Mitsubishi Electric · PUZ-HA30/36NHA4 Outdoor Unit

What does Ud mean?

This fault triggers if the outdoor pipe thermistor (TH1) detects 70°C (158°F) or more during compressor operation. It indicates excessive heat within the outdoor unit, likely due to restricted airflow, a malfunctioning outdoor fan, or a faulty thermistor. Persistent overheating can lead to compressor failure and significant reduction in cooling efficiency.

Repair Steps

  1. 1

    Inspect the outdoor unit's air passage for any obstructions, dirt, or debris.

  2. 2

    Verify proper operation of the outdoor fan motor and fan blades.

  3. 3

    Check the outdoor pipe thermistor (TH1) for correct resistance values and secure connections.

  4. 4

    Turn the unit off and on again. If the error code reappears, address the root cause, possibly replacing the thermistor if it's faulty.

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Verified technical data. Last updated: March 2026
Source: Mitsubishi Electric PUZ-HA30/36NHA4 Outdoor Unit