Fujitsu AOU18RLXFZH 18,000 BTU Multi-Zone Mini Split System with Inverter Compressor 20 Error Fix: Abnormal Indoor Room Temperature Detected

Error code 20 on the Fujitsu AOU18RLXFZH 18,000 BTU Multi-Zone Mini Split System with Inverter Compressor means: Abnormal Indoor Room Temperature Detected. The indoor room temperature sensor is reading a value outside the expected operating range — this can be caused by a faulty thermistor giving an implausible reading, the sensor being exposed to direct sunlight or a heat source, or extreme ambient conditions; verify the sensor is properly positioned and not damaged; compare the sensor reading to actual room temperature with a separate thermometer

The most successful fix is "Test and Replace Faulty Indoor Temperature Sensor Thermistor" (medium difficulty, ~45 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 Faulty Indoor Temperature Sensor Thermistor") is rated medium difficulty and takes about 45 minutes. Tools needed: T20 Torx screwdriver, Digital multimeter, Needle-nose pliers.

DIY cost: $15-$25. Professional repair typically costs $120-$180. Many homeowners save money by trying the top-ranked community fix first.

The Fujitsu AOU18RLXFZH 18,000 BTU Multi-Zone Mini Split System with Inverter Compressor 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 20 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.