ErrorCodeDoctor
Daikin Air Conditioner C9 error code
The C9 error means your Daikin air conditioner detected a fault with the suction air thermistor — the sensor that measures the temperature of the air being drawn into the indoor unit. Without an accurate suction air temperature reading the unit cannot control cooling or heating precisely. Contact a qualified technician.
Common causes
- Suction air thermistor is defective
- Indoor unit PCB has malfunctioned
- Thermistor connector has a poor contact
How to fix it
-
1
Contact a qualified technician to test and replace the suction air thermistor
Related Daikin Air Conditioner error codes
A0
An external protection device connected to the indoor unit has been activated
A1
A fault was detected in the indoor unit PCB (control board)
A3
The drain level control system has detected an abnormality — drain may be clogged
A5
Freeze-up protection (cooling) or high pressure control (heating) has activated — check the air filter
C9 error — frequently asked questions
What does the C9 error mean on a Daikin air conditioner?
The indoor unit suction air thermistor has a fault
What causes the C9 error?
The C9 error is usually caused by: Suction air thermistor is defective; Indoor unit PCB has malfunctioned; Thermistor connector has a poor contact.
Can I fix the C9 error myself?
This is rated a hard fix — it often requires tools, parts, or experience, and may be safer left to a professional technician.
How much does it cost to fix the C9 error?
Fixing the C9 error on a Daikin air conditioner typically costs $80–$250, depending on parts and whether you do it yourself or hire a technician.
Is it safe to keep using my air conditioner with the C9 error?
We'd recommend addressing the C9 error before continuing to use the air conditioner, since hard-rated issues often involve a real fault rather than a minor glitch.