HVAC Error Codes

Searchable Fault Code Database

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All Brands Carrier Trane Lennox Daikin Mitsubishi Electric Fujitsu

Carrier Error Codes

18 codes

Code	Description	Possible Solution
11	No previous fault history	-
12	Blower motor fault	Check blower motor, capacitor, and wiring connections
13	Limit circuit lockout	Check for blocked airflow, dirty filter, or failed limit switch
14	Ignition lockout fault	Check igniter, gas valve, and flame sensor
21	Gas heating lockout	Check gas supply, ignition system
22	Abnormal flame signal	Check flame sensor, clean or replace
23	Pressure switch did not close	Check inducer motor, vent blockage, pressure switch
24	Secondary voltage fuse is open	Check for short in low voltage wiring
25	High stage pressure switch did not close	Check inducer motor, vent blockage
31	Pressure switch did not open	Check pressure switch or hose connections
32	Flame sensed out of sequence	Check gas valve for leakage
33	Limit circuit fault	Check limit switch, airflow, filter
34	Ignition proving fault	Check flame sensor, igniter, gas pressure
41	Blower outside valid speed range	Check blower motor, capacitor
42	Inducer outside valid speed range	Check inducer motor
43	Pressure switch calibration fault	Replace pressure switch
44	Invalid blower airflow selected	Check DIP switch settings
45	Control circuitry lockout	Reset power, may need new control board

Trane Error Codes

11 codes

Code	Description	Possible Solution
1 Flash	System operating normally	-
2 Flashes	System lockout (retries exceeded)	Reset power, check ignition system
3 Flashes	Pressure switch error	Check inducer, venting, pressure switch
4 Flashes	Open temperature limit	Check airflow, filter, limit switch
5 Flashes	Flame sensed when no flame should be present	Check gas valve, flame sensor
6 Flashes	115VAC power reversed or poor grounding	Check wiring polarity
7 Flashes	Gas valve circuit error	Check gas valve wiring
8 Flashes	Igniter circuit error	Check igniter, replace if needed
9 Flashes	Check polarity / grounding	Verify correct line voltage polarity
Continuous ON	Control board failure	Replace control board
Continuous OFF	No 24VAC to control board	Check transformer, wiring

Lennox Error Codes

12 codes

Code	Description	Possible Solution
E1	Open high pressure switch	Check for refrigerant overcharge, dirty condenser, blocked airflow
E2	Open low pressure switch	Check refrigerant charge, indoor coil, filter
E3	Open high pressure switch - compressor 2	Check condenser fan, refrigerant charge
E4	Open low pressure switch - compressor 2	Check refrigerant charge, metering device
E5	High compressor discharge temperature	Check refrigerant charge, TXV, airflow
E6	Outdoor coil temperature sensor fault	Check/replace sensor
E7	Outdoor ambient temperature sensor fault	Check/replace sensor
E8	Suction temperature sensor fault	Check/replace sensor
E9	Discharge temperature sensor fault	Check/replace sensor
E225	Blower motor failure	Check blower motor, capacitor, wiring
E228	Limit switch open	Check airflow, filter, limit switch
E250	Ignition failure	Check igniter, gas valve, flame sensor

Daikin Error Codes

28 codes

Code	Description	Possible Solution
A1	Indoor PCB defective	Replace indoor unit PCB
A3	Drain level abnormal	Check drain pump, drain line, float switch
A5	Freeze-up protection	Check airflow, filter, refrigerant charge
A6	Fan motor abnormality	Check fan motor, capacitor
A7	Swing motor abnormality	Check swing motor, limit switch
C4	Heat exchanger temperature sensor fault	Check/replace thermistor
C5	Condenser temperature sensor fault	Check/replace thermistor
C9	Room temperature thermistor fault	Check/replace thermistor
E1	Outdoor PCB defective	Replace outdoor unit PCB
E3	High pressure switch activated	Check refrigerant charge, condenser coil
E4	Low pressure switch activated	Check refrigerant charge, leaks
E5	Compressor motor overload	Check compressor, capacitor, wiring
E6	Outdoor fan motor lock/overcurrent	Check fan motor, blade obstruction
E7	Outdoor fan motor abnormality	Check fan motor, PCB
F3	Discharge pipe temperature too high	Check refrigerant charge, compressor
F6	Refrigerant overcharge	Recover excess refrigerant
H6	Position sensor abnormality	Check compressor, inverter
H8	DC voltage sensor abnormality	Check inverter board
H9	Outdoor air sensor abnormality	Check/replace thermistor
J3	Discharge pipe thermistor abnormality	Check/replace thermistor
J6	Heat exchanger thermistor abnormality	Check/replace thermistor
L3	Electrical box temperature rise	Check ventilation, wiring connections
L4	Inverter fin temperature rise	Check heat sink, ventilation
L5	Compressor motor insulation short	Replace compressor
P4	Inverter fin temperature sensor fault	Check/replace sensor
U0	Refrigerant shortage	Find leak, recharge system
U2	Power supply voltage abnormality	Check power supply voltage
U4	Communication failure (indoor/outdoor)	Check communication wiring

Mitsubishi Electric Error Codes

25 codes

Code	Description	Possible Solution
E0	Remote controller signal receiving error	Check remote controller, receiver
E1	Remote controller communication error	Check wiring between remote and indoor unit
E2	Indoor/outdoor unit communication error	Check S1/S2 wiring, PCB
E3	Indoor fan motor speed error	Check fan motor, PCB
E4	Room temperature sensor error	Check/replace thermistor
E5	Indoor heat exchanger sensor error	Check/replace thermistor
E6	Freeze-up prevention	Check airflow, filter, charge
E7	Indoor fan motor fault	Check/replace fan motor
E8	Indoor unit EEPROM error	Replace indoor PCB
E9	Indoor/outdoor mismatch	Check unit compatibility
EA	4-way valve fault	Check 4-way valve, coil
Eb	Indoor unit error	Check indoor PCB
F1	Discharge temperature sensor error	Check/replace thermistor
F2	Outdoor heat exchanger sensor error	Check/replace thermistor
F3	Discharge temperature too high	Check charge, compressor
F4	Outdoor air temperature sensor error	Check/replace thermistor
P1	Power supply phase/voltage error	Check power supply
P2	Compressor overcurrent	Check compressor, capacitor
P4	Inverter fin temperature too high	Check ventilation, heat sink
P5	DC voltage error	Check power supply, inverter
P6	Outdoor fan motor abnormality	Check fan motor
U1	High pressure protection	Check condenser, airflow
U2	Low pressure protection	Check refrigerant charge
U3	Compressor overcurrent (startup)	Check compressor, wiring
U4	Compressor overcurrent (running)	Check compressor, charge

Fujitsu Error Codes

25 codes

Code	Description	Possible Solution
E:00	Communication error (serial)	Check wiring, PCB
E:01	Communication error (indoor/outdoor)	Check S1/S2/S3 wiring
E:02	Communication error (wired remote)	Check remote controller wiring
E:03	Communication error (wireless remote)	Check remote, receiver
E:04	Indoor/outdoor unit mismatch	Check compatibility, settings
E:05	Indoor PCB error	Replace indoor PCB
E:06	Indoor fan motor error	Check fan motor, PCB
E:07	Swing motor error	Check swing motor, limit switch
E:08	Room temperature sensor error	Check/replace thermistor
E:09	Indoor coil temperature sensor error	Check/replace thermistor
E:0A	Float switch activated	Check drain pump, drain line
E:0C	Indoor EEPROM error	Replace indoor PCB
E:0E	Address not set	Set unit address
E:11	Outdoor unit model error	Check outdoor unit settings
E:12	Outdoor EEPROM error	Replace outdoor PCB
E:13	Discharge temperature too high	Check refrigerant charge
E:14	High pressure protection	Check condenser, airflow
E:15	Current sensor error	Check outdoor PCB
E:16	Compressor motor lock	Check compressor, wiring
E:17	Outdoor fan motor error	Check fan motor
E:18	Power supply voltage error	Check power supply
E:1A	Outdoor air sensor error	Check/replace thermistor
E:1C	Outdoor coil sensor error	Check/replace thermistor
E:1D	Suction gas sensor error	Check/replace thermistor
E:1E	Discharge gas sensor error	Check/replace thermistor

Detailed Mini-Split Error Code Guides

Complete error code databases with comprehensive troubleshooting for 20 mini-split and inverter AC brands:

Disclaimer

Error codes and solutions are provided for reference only. Always consult manufacturer documentation and service manuals for accurate diagnosis. Error codes may vary by model and firmware version.