ErrorCodeDoctor
Daikin Air Conditioner H9 error code
The H9 error means your Daikin air conditioner detected a fault with the outdoor air thermistor — the sensor that measures the outside air temperature. Without this reading the unit cannot optimise its operation for ambient conditions. Contact a qualified technician to test and replace the outdoor air thermistor.
Common causes
- Outdoor air thermistor connector is loose or disconnected
- Outdoor air thermistor is defective
- Outdoor unit PCB has a fault
How to fix it
-
1
Contact a qualified technician to inspect and replace the outdoor 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
H9 error — frequently asked questions
What does the H9 error mean on a Daikin air conditioner?
The outdoor air thermistor has a fault
What causes the H9 error?
The H9 error is usually caused by: Outdoor air thermistor connector is loose or disconnected; Outdoor air thermistor is defective; Outdoor unit PCB has a fault.
Can I fix the H9 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 H9 error?
Fixing the H9 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 H9 error?
We'd recommend addressing the H9 error before continuing to use the air conditioner, since hard-rated issues often involve a real fault rather than a minor glitch.