HVAC Toolkit
F

Fujitsu Error Codes

Halcyon, Airstage, and Mini-Split Systems

Quick Reference: Error Display Methods

Indoor Unit Display

E#:## format shows on unit display or remote controller

LED Flash Patterns

Count flashes of Operation, Timer, and Economy lights

Outdoor LED1/LED2

Two-digit codes via LED flash sequences

E-Series Errors

Code Description Possible Cause Solution
E0:00 Communication error (remote/indoor) Remote controller communication fault Check remote wiring and connections
E1:00 Indoor/outdoor communication error Signal wire fault between units Check S1/S2/S3 wiring, polarity
E2:00 Return air thermistor error Room temperature sensor open/short Check thermistor resistance, replace if faulty
E3:00 Indoor coil thermistor error Coil temperature sensor fault Check thermistor, verify connection
E4:00 Indoor coil thermistor 2 error Secondary coil sensor fault Check and replace thermistor
E5:00 Drain sensor / float switch error Drain pump or float switch activated Clean drain line, check float switch
E6:00 Outdoor unit error detected General outdoor unit fault Check outdoor unit error codes
E7:00 Indoor fan motor error Fan motor locked or feedback error Check motor windings, PCB, capacitor
E8:00 Indoor unit current overload Indoor PCB drawing excess current Check wiring, reset power
E9:00 Electronic expansion valve error EEV not responding to commands Check EEV coil, wiring, controller
EE:EE EEPROM error Indoor PCB memory fault Replace indoor unit PCB

Outdoor Unit Errors

Code Description Possible Cause Solution
00 Serial communication error Outdoor PCB comm fault Check outdoor unit wiring
01 Inverter board communication error Inverter-to-main PCB fault Check inverter board connections
03 Discharge thermistor error Compressor discharge sensor fault Check and replace thermistor
04 Outdoor coil thermistor error Condenser temp sensor fault Check and replace thermistor
05 Suction gas thermistor error Suction line sensor fault Check and replace thermistor
06 Outdoor ambient thermistor error Outdoor air temp sensor fault Check and replace thermistor
07 Outdoor coil thermistor 2 error Secondary coil sensor fault Check and replace thermistor
08 Compressor inlet thermistor error Compressor inlet sensor fault Check and replace thermistor
09 CT sensor error Current transformer fault Check CT sensor, inverter board
10 Inverter fin thermistor error Heat sink temp sensor fault Check thermistor, inverter board
11 Power transistor thermistor error IPM temp sensor fault Check thermistor, inverter board

Protection Errors

Code Description Possible Cause Solution
12 High pressure protection High discharge pressure Clean condenser, check fan, verify charge
14 Suction pressure low Low refrigerant or restriction Leak test, check charge, inspect TXV
16 ACT over temperature Reactor overheating Check ventilation, reactor condition
17 Discharge temperature high Compressor overheating Check charge, airflow, compressor
19 Condenser temperature high Poor heat rejection Clean condenser, check fan operation
20 Compressor protection Compressor overcurrent/thermal Check compressor, inverter, charge
21 IPM protection (overcurrent) Inverter power module fault Check inverter board, compressor
22 AC overcurrent High AC current draw Check power supply, wiring
23 DC low voltage Low DC bus voltage Check power supply, capacitors
24 DC high voltage High DC bus voltage Check power supply, inverter
25 ACT current error Reactor current abnormal Check reactor, inverter board
27 Pressure sensor error Pressure transducer fault Check pressure sensor, wiring
28 Compressor position error Rotor position feedback fault Check compressor, inverter board
29 Compressor start failure Compressor won't start Check compressor, wiring, inverter
30 Compressor speed error Compressor speed out of range Check inverter board, compressor

System Errors

Code Description Possible Cause Solution
31 Outdoor fan motor error Fan motor lock or speed error Check motor, blade obstruction
32 Outdoor fan motor 2 error Secondary fan motor fault Check motor, wiring
33 Solenoid valve error Solenoid valve not operating Check valve coil, wiring
34 Reversing valve error 4-way valve not shifting Check solenoid coil, verify valve movement
35 Inverter board error Inverter PCB malfunction Replace inverter board
36 Main PCB error Outdoor control board fault Replace outdoor PCB
39 Power supply phase error Phase missing or reversed Check 3-phase power supply

LED Flash Codes (Indoor Unit)

Code Description Possible Cause Solution
Operation Light: 1 Flash Indoor room thermistor error Room temperature sensor fault Check and replace thermistor
Operation Light: 2 Flashes Indoor coil thermistor error Coil temperature sensor fault Check and replace thermistor
Operation Light: 3 Flashes Transmission error Indoor-outdoor communication fault Check signal wiring
Operation Light: 4 Flashes Drain pump error Drain pump or float switch Clean drain, check pump
Operation Light: 5 Flashes Outdoor unit abnormality Outdoor unit fault detected Check outdoor unit error code
Operation Light: 6 Flashes Indoor fan motor error Fan motor not running correctly Check motor, capacitor
Operation Light: 7 Flashes EEPROM error Indoor PCB memory fault Replace indoor PCB
Operation Light: 8 Flashes Freeze/overheat protection Coil temp abnormal Check airflow, filter, charge
Timer Light: Flashing High pressure protection High head pressure Check condenser, fan, charge
Economy Light: Flashing Power supply voltage error Voltage abnormal Check power supply voltage

LED Flash Codes (Outdoor Unit)

Code Description Possible Cause Solution
LED1: 1 Flash High pressure switch open High discharge pressure Check condenser, refrigerant charge
LED1: 2 Flashes Inverter error Inverter protection activated Check inverter board, reset power
LED1: 3 Flashes Indoor/outdoor transmission error Communication fault Check signal wiring connections
LED1: 4 Flashes Outdoor thermistor error Temperature sensor fault Check and replace thermistor
LED1: 5 Flashes CT/DC voltage error Current or voltage sensor fault Check sensors, inverter board
LED2: 1 Flash High discharge temperature Compressor overheating Check charge, suction superheat
LED2: 2 Flashes Outdoor fan motor error Fan motor fault Check motor, PCB
LED2: 3 Flashes Low pressure protection Low refrigerant Leak test, recharge system
LED2: 4 Flashes Compressor error Compressor protection activated Check compressor, inverter

Fujitsu Troubleshooting Tips

Reading Error Codes

  • Wired Remote: Error displays directly on screen
  • Wireless Remote: Press and hold TIMER button for 3 seconds
  • Indoor LEDs: Count flash patterns carefully
  • Outdoor LEDs: LED1 = tens digit, LED2 = ones digit

Most Common Issues

  • E1:00: Communication error - check S1/S2/S3 wiring
  • Error 12: High pressure - clean condenser, check charge
  • Error 20/21: Inverter protection - check compressor
  • E5:00: Drain issue - clean drain line and pump

Clearing Error Codes

  1. Turn off unit at circuit breaker for 30 seconds
  2. Turn power back on
  3. If error persists, the underlying issue must be resolved
  4. Some protection errors (like high pressure) require cooldown period

Daikin Error Codes

Complete Daikin fault code list

Mitsubishi Error Codes

Complete Mitsubishi fault code list

Mini Split Troubleshooting

General troubleshooting guide