Daikin AC error codes – Split / room AC
26 codes from the Daikin service manual, with what each one means and the usual causes. Read the code: hold CANCEL on the remote about 5 s until 00 blinks, press CANCEL repeatedly until a long beep - the code shown then is the fault. Checks are standard Daikin service practice.
You can safely switch the unit off at the switch, wait 5 minutes and switch on again. Don't open the unit, touch wiring or handle gas: these checks need a trained technician.
A1
Indoor PCB fault
What our technician checks
- Power off 3 min and restart.
A5
Freeze-up protection / high pressure control (indoor coil)
What our technician checks
- Indoor filter / coil dirty, blower slow, low gas, very low set temperature with low indoor load.
A6
Indoor fan motor fault
What our technician checks
- Indoor blower turns freely by hand? Blower wheel clean, not rubbing? Fan motor connector, motor supply (AC: capacitor
- DC: about 310 V DC + 15 V and feedback signal).
C4
Indoor heat exchanger sensor fault
What our technician checks
- Indoor coil (pipe) sensor: unplug and measure (commonly 10 kΩ or 5 kΩ at 25°C depending on brand). Check it is clipped into the coil sensor pocket.
C9
Indoor suction (room) air sensor fault
What our technician checks
- Room (return air) sensor: unplug and measure - most split ACs use 10 kΩ at 25°C (about 12.6 kΩ at 20°C, 8 kΩ at 30°C). Open or short = faulty. Check connector on the indoor PCB.
E1
Outdoor PCB fault
What our technician checks
- Power off 3 min and restart.
E5
Compressor overload (OL) - overheated
What our technician checks
- Low refrigerant charge (most common), blocked expansion valve / capillary, EEV not opening, discharge sensor reading wrong.
E6
Compressor start-up failure / lock
What our technician checks
- Compressor windings equal and not earthed? U/V/W lead order and connection. Refrigerant pressures equalised before start? Board output to compressor.
E7
Outdoor DC fan motor fault
What our technician checks
- Outdoor fan turns freely (bearing)? Leaves / debris? DC fan: motor supply from the outdoor PCB and feedback wire.
E8
Input over-current
What our technician checks
- Supply voltage under load, condenser dirty or outdoor fan slow, overcharge, air in system, compressor current against rated.
F3
Discharge pipe temperature too high
What our technician checks
- Low refrigerant charge (most common), blocked expansion valve / capillary, EEV not opening, discharge sensor reading wrong.
F6
High pressure control (cooling)
What our technician checks
- Condenser dirty or air recirculating, outdoor fan slow, overcharge, air / nitrogen in system, valves closed (heating: indoor filter / fan).
H0
Sensor fault (compressor drive sensing)
What our technician checks
- Compressor leads and windings
- board drive section.
H6
Position detection sensor fault - compressor stopped
What our technician checks
- Compressor leads and windings
- board drive section.
H8
DC current sensor fault
What our technician checks
- Current sensing circuit on the outdoor board.
H9
Outdoor air temperature sensor fault
What our technician checks
- Outdoor sensor (ambient / coil / suction): unplug and measure against the brand chart (outdoor ones are usually 10 kΩ, discharge sensors 50-200 kΩ at 25°C).
J3
Discharge pipe sensor fault
What our technician checks
- Discharge pipe sensor: measure (typically 50-200 kΩ at 25°C, brand dependent) and check it is fixed on the discharge pipe.
J6
Outdoor heat exchanger sensor fault
What our technician checks
- Outdoor sensor (ambient / coil / suction): unplug and measure against the brand chart (outdoor ones are usually 10 kΩ, discharge sensors 50-200 kΩ at 25°C).
L3
Electrical box (parts) temperature too high
What our technician checks
- Heat-sink fixing and paste, outdoor airflow, high ambient, heat-sink sensor.
L4
Inverter heat-sink temperature too high
What our technician checks
- Heat-sink fixing and paste, outdoor airflow, high ambient, heat-sink sensor.
L5
Output over-current (compressor / IPM)
What our technician checks
- Power off, wait for capacitors to discharge. Compressor U-V, V-W, W-U equal (about 0.5-3 Ω) and >10 MΩ to earth. Diode test the IPM P/N to U/V/W. Check DC bus (about 310 V DC on 230 V supply), heat-sink paste and screws, condenser cleanliness, supply voltage, overcharge.
P4
Heat-sink temperature sensor fault
What our technician checks
- Outdoor sensor (ambient / coil / suction): unplug and measure against the brand chart (outdoor ones are usually 10 kΩ, discharge sensors 50-200 kΩ at 25°C).
U0
Refrigerant shortage
What our technician checks
- Suction pressure low? Leak test (flare joints, valves, coils) with soap / nitrogen. Valves fully open?
U2
Supply voltage too low / too high
What our technician checks
- Measure mains under load (single phase normally 200-250 V). Loose neutral, undersized cable, stabiliser.
U4
Indoor-outdoor transmission failure
What our technician checks
- Interconnect cable: correct terminal order (L, N, signal, earth), no loose screw or joint, cable not run with other power cables. Is the outdoor unit powered (LED on outdoor PCB)? Signal line voltage fluctuates when healthy. Check outdoor fuse and reactor.
UA
Indoor-outdoor combination mismatch
What our technician checks
- Indoor and outdoor model numbers are a matching pair? Correct capacity / model setting on the board.
Code not here, or still showing?
Send a photo of the display and the model sticker on WhatsApp. We'll tell you what it means and whether it needs a visit.
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