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C4

C4 — Heat exchanger temperature sensor fault

Daikin · Air Conditioner

What does C4 mean?

This code points to an issue with the sensor that measures the temperature of the heat exchanger. Accurate readings are vital for operation.

Common Causes

  • Faulty heat exchanger temperature sensor
  • Loose connection to the sensor

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Inspect the wiring connection to the heat exchanger temperature sensor for security.

  2. 2

    Ensure the sensor itself is not physically damaged.

  3. 3

    A technician may need to test or replace the sensor if the connection is good.

Browse all codes in this manual (40)
Verified technical data. Last updated: April 2026

Related Faults

0000 — Normal operationA1A1 — Indoor unit PCB defect detectedA5A5 — High pressure or freeze-up protector activated
Source: Daikin Air Conditioner
Open Manual (Page 31)Search more codes in this manual