Fujitsu 9,000 BTU 33 SEER Halcyon Wall-Mount Mini Split, WiFi Ready 12 Error Fix: Indoor Pipe (Coil) Temperature Thermistor Error

Error code 12 on the Fujitsu 9,000 BTU 33 SEER Halcyon Wall-Mount Mini Split, WiFi Ready means: Indoor Pipe (Coil) Temperature Thermistor Error. The indoor evaporator coil temperature sensor has an open or short circuit — the sensor is clipped to the indoor heat exchanger coil; check for water damage to the sensor or connector (condensation can corrode connections); measure sensor resistance; if the coil is frozen over, the sensor may be encased in ice causing an abnormal reading — address the root cause of freezing (low refrigerant, dirty filter, low airflow) first

The most successful fix is "Test and Replace Indoor Pipe (Coil) Temperature Thermistor Sensor" (medium difficulty, ~50 minutes). Estimated DIY cost: $15-$25. HomeMD has 2 community-ranked fixes for this error.

This error is rated medium severity. It should be addressed soon, but your appliance may still function in a limited capacity.

Yes — the top-ranked community fix ("Test and Replace Indoor Pipe (Coil) Temperature Thermistor Sensor") is rated medium difficulty and takes about 50 minutes. Tools needed: Phillips screwdriver, Digital multimeter, Needle-nose pliers.

DIY cost: $15-$25. Professional repair typically costs $120-$160. Many homeowners save money by trying the top-ranked community fix first.

The Fujitsu 9,000 BTU 33 SEER Halcyon Wall-Mount Mini Split, WiFi Ready has 8 other known error codes, including: 01 (Indoor Unit PCB Error), 02 (Communication Error — Indoor to Outdoor Unit), 03 (Communication Error — Remote Controller to Indoor Unit), 04 (Outdoor Unit PCB Error), 05 (Outdoor DC Fan Motor Open/Short Circuit), and 3 more.

Error code 12 also appears on 8 other Fujitsu models: 12,000 BTU 18 SEER Slim Duct Mini Split, 8 in Height, Quiet Operation, 12,000 BTU 25 SEER Halcyon Wall-Mount Mini Split with WiFi Control, 15,000 BTU 25 SEER Halcyon Wall-Mount Mini Split with Energy Saving Mode, 24,000 BTU 19 SEER Wall-Mount Mini Split with Low Ambient Cooling, 36,000 BTU 18 SEER Multi-Zone Heat Pump Outdoor Unit, 48,000 BTU Multi-Zone Heat Pump Outdoor Unit, and 2 more. The fix may vary by model, so check each model's specific page for tailored repair steps.