Daikin Mini-Split Code J3
Warning
Discharge pipe thermistor or related abnormality. The compressor discharge sensor is open or shorted, or it is reading colder than the heat exchanger, which is physically impossible.
Manual wording: “J3 Discharge pipe thermistor or related abnormality”
Documented for: RKS/RXS pair outdoor units, FTXM-W/V outdoor units, RMXS multi-split outdoor
Likely causes, most common first
- Disconnection of the connector for the thermistor
- Defective discharge pipe thermistor
- Defective heat exchanger thermistor (outdoor coil in cooling, indoor coil in heating)
- Defective outdoor unit PCB
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
A discharge sensor that has slipped out of its holder or failed has to be reseated or replaced by a technician - running without it risks overheating the compressor.
A Daikin mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Service Manual - Inverter Pair FTXS-L Series / FDXS-L Series (SiUS091133) (Daikin, FTXS09/12/15/18/24/30/36LVJU wall mount, FDXS09/12LVJU ducted, RKS/RXS09-36LVJU outdoor) · checked 2026-08-25
- Service Manual - Inverter Pair Wall Mounted Type H-Series (SiUS04-924_A) (Daikin, FTXS30/36HVJU indoor, RKS30/36HVJU and RXS30/36HVJU outdoor) · checked 2026-08-25
- Service Manual - Inverter Pair Wall Mounted Type FTXM-W/V Series (SiUS042113EA) (Daikin, FTXM-W / FTXM-V (Daikin Atmosphera) wall-mount heat pump) · checked 2026-08-25
- 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