P6

Coil Frost/Overheating Protection Abnormality

Mitsubishi Electric · R410A Systems

What does P6 mean?

The indoor unit's protection mechanisms for evaporator coil frost or overheating are malfunctioning. This could lead to evaporator coil icing in cooling mode or excessive coil temperatures in heating mode, impacting efficiency and potentially damaging components.

Common Causes

  • Coil frost protection activated (overheating or freezing).
  • Abnormal coil temperature detected.
  • Airflow obstruction or refrigerant issue causing frost/overheating.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Verify the indoor pipe sensor (P2) is operating correctly by measuring its resistance.

  2. 2

    Check indoor fan motor operation and ensure adequate airflow across the evaporator coil.

  3. 3

    Inspect the outdoor unit for issues affecting refrigerant pressures, such as low charge (for frosting) or high pressure (for overheating).

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Verified technical data. Last updated: March 2026

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Source: Mitsubishi Electric R410A Systems