Radiation Fin (Heat Sink) Temperature Rise

What it means

This code appears on Daikin inverter split, ducted and cassette air conditioners and means the radiation fin (heat sink) that cools the power module (IPM) on the outdoor board has risen above its safe temperature. The unit stops the compressor to protect the electronics, which happens most in very hot weather. 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.

Related codes: P4E7F6L5

Symptoms4

• The compressor stops and L4 appears, usually in the afternoon.
• The unit restarts after cooling down, then trips again.
• Weak cooling in extreme heat.
• The outdoor unit casing feels very hot.

Possible causes6

• Poor airflow around the outdoor unit from dust, leaves or a bad location.
• A failed or weak outdoor fan.
• Very high outdoor temperatures with the unit in direct sun in an enclosed space.
• Poor contact between the power module and the heat sink from dried thermal paste or loose mounting.
• High compressor load from high pressure or a refrigerant circuit problem.
• A faulty fin thermistor or board.

How to diagnose5

1. Switch the unit off and make sure the outdoor unit is clean with enough clearance for airflow.
2. Note whether the code only appears in the hottest hours.
3. A technician confirms the outdoor fan speed.
4. The technician checks the power module mounting on the heat sink after isolating power and discharging the board.
5. The technician measures operating pressures and compressor current, and checks the fin thermistor reading against the Daikin table.

How to fix5

1. Wash the outdoor unit and remove anything blocking airflow.
2. Improve the outdoor unit location or shade it without restricting airflow.
3. Repair the outdoor fan or replace its motor.
4. Remount the power module on the heat sink with fresh thermal paste where the model allows, or replace the outdoor board.
5. Test the unit in hot weather and confirm the code does not return.

Repair cost

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

Cleaning the outdoor unit and improving ventilation solve many cases at moderate cost; a fan motor raises the cost, and the top of the range applies when the outdoor board must be replaced.

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