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C9

C9 - Return air sensor fault

Daikin · Air Conditioning

What does C9 mean?

The sensor measuring the temperature of the air returning to the unit is open or short circuited.

Common Causes

  • Return air sensor is open or short circuited.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Locate the return air sensor and check its connection.

  2. 2

    Inspect the sensor and its wiring for any damage.

  3. 3

    A faulty sensor or wiring will need to be replaced by a qualified technician.

Browse all codes in this manual (79)
Verified technical data. Last updated: April 2026

Related Faults

A0A0 - External protection activeA1A1 - Indoor PCB failureA2A2 - Malfunction of freezing protection
Source: Daikin Air Conditioning
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