Radiation Fin Thermistor Abnormality

Home Appliance Error Codes Daikin Split AC

Can you still use it? No, unplug it

Who can fix it? Needs an authorized technician

Typical repair time 30 minutes – 3 hours

Typical cost SAR 80 to 2,500

What it means

This code appears on Daikin inverter split, ducted and cassette air conditioners and means the sensor that measures the radiation fin (heat sink) temperature of the power module on the outdoor board is reading implausibly because of an open or short circuit. Without this reading the board cannot protect itself from overheating, so the compressor stops. The same code can mean something else on other brands.

Models covered: Daikin split air conditioners and Daikin ducted/cassette (SkyAir) units, which share the same error code system; the code shows on the wired remote or via the wireless remote check function.

Symptoms3

Code P4 appears and the compressor does not run.
The code may appear at startup or shortly after.
No cooling until the cause is fixed.

Possible causes4

A failed sensor, which on many models is built into the power module or mounted on the outdoor board.
A loose or corroded connector on models where the sensor is separate.
Moisture, insects or burn marks on the outdoor board.
A faulty sensor input circuit on the board.

How to diagnose5

Switch the unit off at the breaker for several minutes, then restart.
A technician inspects the outdoor board after isolating power and discharging it.
The technician checks the Daikin service manual for the model to see whether the sensor is separate or built into the board.
If it is separate, the technician measures its resistance against the manufacturer table and checks its connector.
If it is built in and the code persists after the connections are checked, the board is condemned.

How to fix5

Clean dust and insects from the board and dry it if moisture is found.
Reseat or replace a separate fin thermistor.
Replace the outdoor PCB if the sensor is built into it or its input circuit is proven faulty.
Make sure the fan and ventilation are good so the new board is not overheated.
Run and test the unit and confirm the code does not return.

Repair cost

0–200

200–600

600–1,500

1,500+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low on models with a separate sensor, but on many inverter models the sensor is part of the outdoor board, so the price rises to that of the board.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions

What is the difference between P4 and L4?

L4 means the fin temperature really is too high, while P4 means the sensor measuring it has failed and gives an implausible reading.

Why does the technician recommend a whole new board?

On many inverter models the sensor is built into the power module or mounted on the board and is not sold separately, so replacing the board is the approved repair.

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This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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