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Aircon Error Codes: Daikin

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Daikin Air Conditioner Error Codes: Common Codes and What to Do

Error codes showing up in your Daikin air conditioner is the system’s way of flagging a fault. In this page, we cover common Daikin error codes and the basic checks you can safely try before booking a technician.

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Air Care Solutions services Daikin AC systems (split, ducted, and commercial) across Sydney and NSW.

Important Safety Notes Before Troubleshooting

Before performing troubleshooting, remember these tips:

Do not remove panels or access wiring.
Do not attempt DIY electrical repairs.
If needed, turn the AC unit off at the isolator and wait a few minutes before restarting.
If you smell burning, hear buzzing, see smoke, or the system keeps tripping power, turn the AC off and call a technician immediately.

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A Homeowner’s Guide to Common Daikin Error Codes

Below are common Daikin AC error codes that customers frequently see. We have included what the code usually means, the most likely causes, and which types of units the issues usually appear on.

Important note: Some codes relate to sealed refrigerant systems, compressors, or internal electronics. If basic checks don’t clear the error, it’s best to book a professional diagnosis and repair.

Error Code	What It Means	Common Causes	Common On:
A6	Indoor fan motor problem	Fan motor fault, loose wiring/connection, indoor circuit board issue	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Heat Reclaim Ventilator
C4	Sensor fault on the indoor heat exchanger (liquid pipe)	Sensor failure, loose connection, indoor circuit board issue	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Heat Reclaim Ventilator ‣ Chiller ‣ Fan Coil
C5	Sensor fault on the indoor heat exchanger (gas pipe)	Sensor failure, loose connection, indoor circuit board issue	‣ Split/Multi-split ‣ VRV ‣ Packaged ‣ Heat Reclaim Ventilator ‣ Chiller
C9	Indoor air temperature sensor problem	Sensor failure, loose connection, indoor PCB issue	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Heat Reclaim Ventilator ‣ Fan Coil
E3	High-pressure protection has activated	Dirty outdoor coil, blocked airflow, refrigerant restriction, pressure switch fault	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
E4	Low-pressure protection has activated	Low refrigerant, pressure sensor fault, outdoor PCB issue	‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
E5	Compressor or inverter is overheating, or a motor fault	Compressor strain/lock, inverter PCB fault, wiring connection issue	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
E6	Compressor overcurrent or the compressor is locked	Compressor fault, PCB fault, stop valve closed (installation issue)	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
E7	Outdoor fan motor system problem	Fan motor fault, wiring/connector issue, obstruction stopping fan blades	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
E8	Inverter compressor overcurrent	Compressor fault, capacitor issue, PCB/power transistor fault	‣ Split/Multi-split ‣ Chiller
F3	Discharge pipe temperature fault	Sensor failure, abnormal discharge temperature, outdoor PCB issue	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
L5	Inverter overcurrent (protection fault)	Compressor wiring fault, mechanical lock, inverter PCB fault	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
U0	Refrigerant issue (often low refrigerant)	Refrigerant leak/shortage, wrong piping, sensor/pressure fault	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller
U2	Power supply issue or brief power failure	Voltage fluctuation, momentary outage, wiring fault	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller ‣ Fan Coil
U4	Communication issue between indoor and outdoor units	Wiring fault, outdoor unit power off, incorrect addressing, PCB fault	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Heat Reclaim Ventilator ‣ Chiller ‣ Fan Coil
U5	Communication issue between indoor unit and remote controller	Remote/controller wiring issue, signal noise, PCB fault	‣ Split/Multi-split ‣ SkyAir ‣ VRV ‣ Packaged ‣ Chiller ‣ Fan Coil

Quick tip: If an error code clears after cleaning fliters and power cycling, but returns within 24-48 hours, it’s usually a sign of an underlying fault and not just a one-off interruption.

What the Codes Generally Mean

Fan and airflow faults (A6, E7): These are usually triggered strongy restricted airflow, dirty filters, or a fan not running correctly.
Sensor faults (C4, C5, C9, F3): This is usually a failed temperature sensor or a connection issue that typically requires a technician if they keep returning.
Pressure faults (E3, E4, U0): These may stronge caused strongy stronglocked airflow, strongut are often due to refrigerant or system restrictions.
Compressor and inverter faults (E5, E6, E8, L5): These error codes require professional diagnosis and repair.
Communication faults (U4, U5): These are often caused strongy power issues, wiring faults, or controller/PCstrong prostronglems.
Power supply faults (U2): Common after storms, outages, or unstastrongle voltage.

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Troubleshooting Steps to Fix Common Error Codes

If you’d like to try resolving error codes on your own, you can proceed with the following safe checks before calling a professional.

1. 1) Reset the AC system safely
- Turn the system off at the controller.
- Switch it off at the isolator/breaker.
- Wait for 3-5 minutes.
- Turn the power back on and restart.
2. Clean or replace the filters

Dirty filters are one of the leading causes of airflow restriction and can contribute to pressure and fan-related error codes.
3. Check the outdoor unit has clear airflow

Clear away leaves, debris, and objects. A blocked outdoor unit can trigger pressure and overheating codes.
4. Check vents and return air are not blocked

A blocked supply vent or return air grills can cause the system to overwork and trigger protection faults.
5. Check the remote controller (if applicable)

Replace batteries, and ensure that the settings (mode/temp/fan) are correct. Communication issues (U5) can also be triggered by controller problems.

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When to Call a Professional Technician

Some Daikin error codes must be treated as a sign to book a licensed technician, especially when they involve repairs for compressors, inverters, pressure faults, or internal electronics.

Book a repair if:

The same code returns after resetting the AC system.
The system won’t cool or heat properly.
The outdoor unit isn’t running normally, or the breaker trips repeatedly.
There is a burning smell, buzzing, or visible damage.
You hear odd noises from the outdoor unit.

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Aircon Error Codes: Daikin

Daikin Air Conditioner Error Codes: Common Codes and What to Do

A Homeowner’s Guide to Common Daikin Error Codes

What the Codes Generally Mean

Troubleshooting Steps to Fix Common Error Codes

1. 1) Reset the AC system safely

2. Clean or replace the filters

3. Check the outdoor unit has clear airflow

4. Check vents and return air are not blocked

5. Check the remote controller (if applicable)

When to Call a Professional Technician

The same code returns after resetting the AC system.

The system won’t cool or heat properly.

The outdoor unit isn’t running normally, or the breaker trips repeatedly.

There is a burning smell, buzzing, or visible damage.

You hear odd noises from the outdoor unit.

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What Our Sydney Clients Say

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