Daikin Error Code C9: Suction Air Thermistor Fault
Warning: Your Daikin HVAC system has detected a fault with the suction air thermistor. It's safe to operate, but you should schedule a professional repair soon.
How to Fix Daikin Code C9
- Turn off your HVAC system at the thermostat to prevent further wear.
- Contact a Daikin professional for repair. They have the tools and expertise to diagnose and fix the issue safely.
How to Reset Daikin Code C9
- Turn off the unit using the remote control or wall controller.
- Turn off the circuit breaker for the outdoor and indoor units. Wait 60 seconds.
- Restore power at the breaker.
- Turn the unit on with the remote control. If the error returns, the fault needs professional diagnosis.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Daikin Error Code C9 Mean?
The Daikin C9 error indicates a problem with the suction air thermistor, a temperature sensor that helps regulate your HVAC system's performance. This issue doesn't pose an immediate safety risk, but it can lead to reduced comfort and system efficiency if left unaddressed. The thermistor might be faulty or the wiring could be damaged.
Common Causes
- Faulty suction air thermistor
- Damaged or loose wiring
- Dirty or blocked thermistor
- Incorrect thermistor installation
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| System is running | Measure the resistance of the suction air thermistor using a multimeter. It should be between 10,000 to 100,000 ohms at 77°F (25°C). | — |
| Thermistor resistance is out of range | Inspect the wiring for any damage, corrosion, or loose connections. | — |
Applicable Daikin Models
- Daikin Comfort(electric)
- Daikin Fit(electric)
- Daikin Intelligent Touch(electric)
- Daikin Latitude(electric)
- Daikin Unitary System(electric)
- FIT(electric)
- Inverter Ducted Split System(electric)
- LV Series(electric)
- MXS(electric)
- Multi-Zone(electric)
- NCB(electric)
- NCM(electric)
- NCV(electric)
- NCW(electric)
- NMB(electric)
- NMP(electric)
- NPE(electric)
- NTV(electric)
- NW(gas)
- NWZ(dual_fuel)
- Quaternity(electric)
- SkyAir(electric)
- VRV(electric)
- VRV IV(electric)
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Suction Air Thermistor | 42576C0002 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Daikin model families as C9.
| Code | Description | Severity |
|---|---|---|
| A1 | Indoor PCB Defective | Warning |
| A3 | Drain Level System Fault | Warning |
| A5 | Freeze-Up/Overheat Protection | Warning |
| A6 | Fan Motor Lock/Overcurrent | Warning |
| C4 | Heat Exchanger Thermistor Fault | Warning |
| E1 | Outdoor PCB Defective | Warning |
| E3 | High Pressure Switch Activated | Warning |
| E4 | Low Pressure Switch Activated | Warning |
| E5 | Compressor Motor Lock | Warning |
| E6 | Standard Compressor Motor | Warning |