Daikin Air Conditioner Error C9

⚡ Quick Answer: The Daikin Air Conditioner C9 error indicates a communication failure between the indoor and outdoor units, primarily due to a fault in the indoor uni... ✅ DIY Fixable

What Does Error C9 Mean?

The Daikin Air Conditioner C9 error indicates a communication failure between the indoor and outdoor units, primarily due to a fault in the indoor unit's suction air temperature sensing system. This can result from a malfunctioning suction air thermistor, poor wiring connections, or issues with the indoor unit's control PCB. When this error occurs, the air conditioner may stop operating and fail to produce cool or warm air, often accompanied by a flashing display.

Common Symptoms:

  • Indoor unit stops operation when C9 displays
  • Air conditioner may not produce cool/heat air
  • Error code displayed on remote or unit indicating sensor fault

Possible Causes

  • Faulty suction air thermistor (high)
  • Poor connection or wiring issue at the thermistor connector (medium)
  • Indoor unit control PCB processing error of thermistor signal (medium)

How to Fix Error C9

DIY Fix Basic power reset and check environmental conditions

  1. Turn off the air conditioner and cut power at the breaker or unplug the unit
  2. Wait approximately 1 minute
  3. Restore power and attempt to restart to see if the error clears
  4. Ensure air intake and filters are clean and unobstructed

Technician Only Inspect and replace suction air thermistor and associated wiring

  1. Disconnect power to the unit
  2. Remove indoor unit cover to access suction air thermistor
  3. Test thermistor resistance and verify against spec
  4. Check and secure thermistor connector and wiring integrity
  5. Replace thermistor if out of specification
  6. If thermistor and wiring are correct, test and inspect indoor control PCB for faults

Parts needed: Suction air thermistor, Thermistor wiring/connector, Indoor unit PCB (if required)

🛑 When to Call a Pro:
  • If the error persists after basic power reset and cleaning
  • If thermistor or PCB testing tools are not available to the technician
  • If signs of electrical damage are present

Technical Specifications

wattage N/A
component Control Board
resistance N/A
part_number DAIKIN 4A118A
voltage_rating 230V AC

Common Questions

What does C9 error mean on Daikin Air Conditioner?

C9 indicates a communication failure linked to a faulty suction air thermistor, causing the unit to stop working.

Can I fix Daikin Air Conditioner C9 error myself?

Yes, you can try a basic power reset by turning off the unit and restoring power after one minute.

How much does it cost to fix C9 error?

Repair costs typically range from $50 to $300+, depending on parts and labor.

When should I call a technician for C9?

Call a technician if the error persists after a reset, or if you lack the tools for testing components.

Sources & References

Data last verified: 2026-07-01

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