HVAC Toolkit
D

Daikin Error Codes

Mini-splits, VRV/VRF Systems, and Air Conditioners

Quick Reference: Error Code Prefixes

A_ Indoor Unit
C_ Sensors
E_ Outdoor Unit
F_/H_ Protection
J_ Thermistors
L_/U_ System/Inverter

A-Series (Indoor Unit Issues)

Code Description Possible Cause Solution
A0 External protection device activated External protection circuit open Check external protection device, reset if tripped
A1 Indoor unit PCB defective PCB malfunction or failure Reset power; if persists, replace indoor PCB
A3 Drain level abnormal Clogged drain, failed pump, or float switch activated Clear drain line, check pump, clean float switch
A4 Heat exchanger abnormality Temperature sensor malfunction or coil issue Check heat exchanger thermistor, clean coil
A5 Freeze-up protection activated Low airflow, dirty filter, low refrigerant Clean filter, check blower, verify refrigerant charge
A6 Indoor fan motor abnormality Motor overload, locked rotor, or wiring issue Check motor windings, capacitor, and wiring
A7 Swing motor abnormality Louver motor stuck or limit switch failure Check swing motor operation, reset louver position
A8 AC input overcurrent Power supply issue or internal short Check power supply voltage and wiring
A9 Electronic expansion valve failure EEV motor or coil failure Check EEV operation, replace if stuck
AA Heater overheat Auxiliary heater overtemperature Check heater element and thermostat
AH Air filter clogged Dirty air filter detected Clean or replace air filter
AJ Capacity setting error Incorrect capacity jumper or DIP switch Verify capacity settings match unit specifications

C-Series (Sensor Issues)

Code Description Possible Cause Solution
C4 Indoor heat exchanger thermistor fault (liquid) Open, short, or out of range thermistor Check resistance, replace thermistor if faulty
C5 Indoor heat exchanger thermistor fault (gas) Open, short, or out of range thermistor Check resistance, replace thermistor if faulty
C7 Louver motor position sensor fault Position sensor failure Check sensor wiring, replace louver motor
C9 Room temperature thermistor fault Open, short, or out of range thermistor Check room sensor, replace if necessary
CA Discharge air thermistor fault Thermistor malfunction Check and replace thermistor
CC Humidity sensor fault Humidity sensor failure Check and replace humidity sensor
CE Radiant temperature sensor fault Sensor malfunction Check and replace sensor

E-Series (Outdoor Unit Issues)

Code Description Possible Cause Solution
E0 Protective device activated Safety device tripped Identify which protection device, reset if safe
E1 Outdoor unit PCB defective PCB malfunction or failure Check for burnt components, replace outdoor PCB
E3 High pressure switch activated High head pressure - dirty coil, overcharge, failed fan Clean condenser coil, check fan, verify charge
E4 Low pressure switch activated Low refrigerant, restriction, or failed compressor Check for leaks, verify refrigerant charge
E5 Compressor motor overload Motor overload due to mechanical or electrical issue Check compressor windings, run capacitor, amp draw
E6 Outdoor fan motor lock/overcurrent Fan motor stuck or drawing excessive current Check for obstruction, test motor windings
E7 Outdoor fan motor abnormality Fan motor or PCB fault Check fan motor, replace if faulty
E8 Compressor overcurrent High amp draw, mechanical failure Check compressor, refrigerant charge, voltage
E9 Electronic expansion valve abnormality EEV not responding to commands Check EEV coil and wiring, replace if stuck
EA 4-way valve abnormality Reversing valve not shifting Check solenoid coil voltage, verify valve movement
EC Abnormal water temperature Water temperature out of range (chiller/heat pump) Check water flow, heat exchanger
EE Water leakage in outdoor unit Drain pan overflow or leak detected Check drain, fix leak source
EF Ice making unit abnormality Ice maker fault (VRV system) Check ice making unit components

F-Series (Protection Codes)

Code Description Possible Cause Solution
F3 Discharge pipe temperature too high Low charge, restriction, or compressor issue Check refrigerant charge, inspect compressor
F6 Refrigerant overcharge / high pressure Too much refrigerant or condenser restriction Verify charge, clean condenser coil

H-Series (System Issues)

Code Description Possible Cause Solution
H0 Sensor abnormality General sensor fault detection Check all sensors in system
H1 Humidity sensor abnormality Outdoor humidity sensor failure Check and replace sensor
H3 High pressure switch stuck HP switch not resetting properly Replace high pressure switch
H4 Low pressure switch stuck LP switch not resetting properly Replace low pressure switch
H6 Compressor position sensor abnormality Inverter compressor position feedback fault Check inverter board and compressor
H7 Outdoor fan position sensor abnormality DC fan motor feedback fault Check fan motor and wiring
H8 DC voltage/current sensor abnormality Inverter sensor fault Check inverter board
H9 Outdoor air temperature thermistor fault Ambient sensor failure Check and replace thermistor
HA Discharge air temperature thermistor fault Thermistor at compressor discharge Check and replace thermistor

J-Series (Thermistor Codes)

Code Description Possible Cause Solution
J3 Discharge pipe thermistor abnormality Thermistor open, short, or out of range Check thermistor resistance, replace if needed
J5 Suction pipe thermistor abnormality Thermistor fault Check and replace suction thermistor
J6 Outdoor heat exchanger thermistor fault Coil sensor failure Check and replace thermistor
J7 Heat exchanger thermistor abnormality (sub) Secondary coil sensor failure Check and replace thermistor
J8 Liquid pipe thermistor fault Thermistor malfunction Check and replace thermistor
J9 Sub heat exchanger gas side thermistor Thermistor failure Check and replace thermistor
JA High pressure sensor abnormality Pressure transducer fault Check sensor, calibrate or replace
JC Low pressure sensor abnormality Pressure transducer fault Check sensor, calibrate or replace

L-Series (Protection Codes)

Code Description Possible Cause Solution
L0 Inverter system malfunction Inverter protection activated Check inverter board, reset power
L1 Inverter PCB defective Inverter board failure Replace inverter PCB
L3 Electrical box temperature rise Poor ventilation or high ambient Check unit location, clean vents
L4 Inverter heat sink temperature rise Heat sink overtemperature Check for airflow blockage, clean heat sink
L5 Compressor motor insulation fault Short circuit in compressor winding Megohm test compressor, replace if failed
L6 Compressor motor lock Mechanical failure or high pressure Check pressures, test compressor
L7 Total motor current too high Overcurrent condition Check motor loads and voltages
L8 Compressor overcurrent (quick trip) Instantaneous overcurrent Check compressor and power supply
L9 Compressor startup failure Compressor won't start Check compressor, wiring, capacitor
LA Power transistor abnormality IGBT or transistor failure Replace inverter board
LC Communication error between inverters Inverter-to-inverter comm fault Check wiring between boards

P-Series (Sensor Protection)

Code Description Possible Cause Solution
P1 Power supply phase abnormality Phase missing or reversed Check 3-phase power supply
P3 Electrical box temperature thermistor fault Thermistor failure Check and replace thermistor
P4 Inverter fin temperature thermistor fault Heat sink sensor failure Check and replace sensor

U-Series (System Faults)

Code Description Possible Cause Solution
U0 Refrigerant shortage / low pressure Refrigerant leak or low charge Leak test system, repair and recharge
U1 Phase reversed / missing phase Power supply wiring error Check and correct phase sequence
U2 Power supply voltage abnormality Voltage too high or too low Measure voltage, correct power supply
U3 Communication error (transmission check) Signal transmission failure Check wiring connections
U4 Communication error (indoor-outdoor) No communication between units Check signal wiring, S1/S2 connections
U5 Communication error (remote controller) Remote wiring or PCB issue Check remote wiring F1/F2
U7 Communication error (master-slave) Multi-unit communication fault Check addressing and wiring
U8 Communication error (sub remote) Secondary remote fault Check sub-remote wiring
U9 Communication error (same address) Duplicate address detected Check and correct unit addresses
UA Communication error (combination) Mismatch of indoor/outdoor units Verify compatible unit combination
UC Centralized address duplication BACnet or central control addressing Check central control settings
UE Communication error (indoor-centralized) Central controller communication Check BMS wiring and settings
UF Wiring error / unit mismatch Incorrect system wiring Verify all wiring connections

Daikin Troubleshooting Tips

Reading Error Codes

  • Error codes display on indoor unit LED panel or wired remote
  • Some units use flashing LED patterns (count flashes)
  • VRV systems store fault history - access via service mode
  • U0 and U4 are most common - check refrigerant and wiring first

Common Issues

  • U0: Most common - usually refrigerant leak
  • U4: Communication error - check S1/S2 wiring
  • A3: Drain issue - clean drain line and pan
  • E3/E4: Pressure switch - check refrigerant charge

Before Calling for Service

  • Turn off unit, wait 5 minutes, then restart - some errors auto-reset
  • Check and clean air filters - many errors caused by restricted airflow
  • Verify power supply voltage is within specification
  • Check circuit breaker and disconnect switch
  • Note the exact error code and when it occurs for technician

Mitsubishi Error Codes

Complete Mitsubishi fault code list

Fujitsu Error Codes

Complete Fujitsu fault code list

Mini Split Troubleshooting

General troubleshooting guide