Daikin · Air Conditioner error code

L4Inverter heat sink overheating

Cross-checked High-voltage / caution

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

Related diagnostic guides

Guide · Air Conditioner

AC/heat pump outdoor fan not spinning

On conventional units the usual causes are a failed fan capacitor, a seized motor or a contactor problem. On inverter mini-splits the fan is driven by the board and usually posts a fan error code.

5 steps ~45 minmoderate

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PTAC not heating (electric heat or heat pump)

PTACs heat with electric strip heat, a heat pump, or both. Heat pump models switch to strip heat in cold weather. Check settings, then the heater element and its limits, then the reversing valve.

5 steps ~60 minmoderate

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Air conditioner running but not cooling enough

Most no-cool calls on room units are airflow, installation or sizing problems, not hardware. Measure the temperature drop across the unit first, then work through filter, coils, air leaks and heat load before suspecting the sealed system.

6 steps ~30 mineasy