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P4

Daikin Split AC

Severity: Moderate

Source: OnlyErrorCodes.com — Every error code. One place.

Daikin AC P4 Error — Radiation Fin Sensor

What Does This Error Mean?

P4 on a Daikin AC means the radiation fin (heat sink) temperature sensor on the inverter board has faulted — open or short circuit. The inverter cannot monitor its own cooling. The unit shuts down to prevent overheating damage. Sensor or board replacement is needed.

Affected Models

  • Daikin FTKF Series
  • Daikin FTKG Series
  • Daikin ATKF Series
  • Daikin FTXM Series
  • Daikin Inverter Split AC (all models)

Common Causes

  • Failed radiation fin temperature sensor (NTC thermistor)
  • Sensor wiring loose at the inverter board connector
  • Damaged sensor pins from rough handling during a previous service
  • Inverter board fault affecting sensor input
  • Moisture ingress at the sensor housing

How to Fix It

  1. Power off the AC for 30 minutes.

    A long power-off allows the sensor to cool and the inverter to reset. Some P4 events from temporary high temperatures clear after cooling.

  2. Clear airflow obstructions at the outdoor unit.

    While P4 is a sensor fault, restricted airflow can cause real overheating that damages the sensor over time. Clean the outdoor coil and ensure 30 cm minimum clearance on all sides.

  3. Restart and watch.

    Restore power and run a short cooling cycle. If P4 clears and the AC works normally, the cause was a transient fault. If P4 returns immediately or after a few minutes, the sensor is faulty.

  4. Book Daikin service for sensor replacement.

    Sensor parts cost USD 30–60. Labour adds USD 150–250 because the technician must access the outdoor electrical box. Total typical cost USD 200–300 fitted.

  5. Confirm board health during service.

    Ask the technician to check the inverter board for damage from any previous overheating. P4 sometimes accompanies marginal board damage — fixing both at once avoids a return visit.

When to Call a Professional

P4 requires opening the outdoor electrical compartment to access the sensor. Book Daikin-authorised service — DIY here risks both component damage and electrical hazards.

Frequently Asked Questions

Will P4 damage my Daikin AC?

P4 itself is a protection fault — it shuts down the unit before damage occurs. However ignoring P4 (forcing restart) bypasses the protection and risks real overheating damage. Always resolve P4 properly.

Can I keep using my Daikin AC with P4?

No — P4 prevents starting. The inverter cannot operate safely without temperature monitoring. Wait for service rather than attempting workarounds.