Daikin Mini-Split Code J9
Warning
Subcooling heat exchanger gas pipe thermistor (R6T) abnormality. That sensor read open or shorted.
Manual wording: “J9 Subcooling heat exchanger gas pipe thermistor (R6T) abnormality”
Documented for: RMXS multi-split outdoor units
Likely causes, most common first
- Disconnection of thermistor
- Defective subcooling heat exchanger gas pipe thermistor (R6T)
- Defective main PCB (A1P)
What you can safely check yourself
- Turn the system off at the breaker or disconnect switch and back on once
When to call a technician
Sensor replacement inside the outdoor unit is a technician job.
A Daikin mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Service Manual - Multi-Split Type Air Conditioners RMXS-L Series (SiUS181631EA) (Daikin, RMXS48LVJU outdoor, BPMKS048A2U/049A3U branch provider, CTXG/CTXS/FTXS/CDXS/FDXS/FVXS/FFQ indoor units) · checked 2026-08-25