Daikin air conditioner Error Codes

Q: What are Daikin AC error codes and how does the system generate them?

Daikin AC error codes are alphanumeric fault indicators generated by the system's internal control board when it detects an operating condition outside the acceptable range. The system continuously monitors refrigerant pressure, component temperatures, electrical current, fan speeds, and communication signals. When any of these readings exceeds or falls below the defined threshold, the control board logs a fault event and displays the corresponding code on the indoor unit display, wired controller, or via the remote control indicator. Each code corresponds to a specific fault category, allowing a technician to identify the area of the system that needs attention.

Q: How do I fix Daikin AC error codes at home?

A small number of Daikin error codes can be addressed by the homeowner without professional assistance. An A5 code triggered by a dirty filter can often be resolved by cleaning the return air filter and allowing the system to reset. An A3 float switch code can be partially addressed by checking and emptying the condensate drain pan. An E3 high pressure code may improve if debris is cleared from around the outdoor unit. All other codes, particularly E4, U4, A1, E1, and all C and H series sensor codes, require a certified Daikin technician with the appropriate diagnostic tools and refrigerant handling certification.

Q: How do I reset a Daikin AC error code properly?

To reset a Daikin AC error code, first note the code displayed, then address any obvious contributing cause such as cleaning the filter or clearing obstruction from the outdoor unit. Switch the unit off at the remote, then turn the circuit breaker for the air conditioner to the off position and wait thirty seconds before restoring power. Wait a further two minutes before restarting the unit. If the same code reappears within thirty minutes of operation, the underlying fault has not been resolved and a certified Daikin technician in Melbourne needs to diagnose the system. Repeated resets without resolving the fault can cause additional damage to the compressor or inverter.

Q: Why does my Daikin AC keep showing the same error code after being reset?

A Daikin air conditioner that displays the same error code after every reset is detecting the same fault condition each time it operates. The reset clears the live error indicator but does not change the physical condition that triggered it. For example, if the E4 code returns after every reset, the refrigerant pressure is still below the safe threshold because the leak that caused the low pressure has not been repaired. A code that persists through multiple resets requires a certified Daikin technician to diagnose and resolve the root cause, not additional resets.

Q: Which Daikin error codes are the most serious and require urgent repair?

The Daikin error codes that warrant the most urgent attention are E4 and U0, which indicate low refrigerant and risk compressor damage if the system continues to run, E5 and E6, which indicate compressor electrical faults that can escalate to compressor failure, A1 and E1, which indicate PCB faults that can cause secondary component damage if ignored, and U4, which indicates a communication failure that prevents safe coordinated operation between the indoor and outdoor units. If any of these codes appear, switch the system off and contact a certified Daikin technician in Melbourne promptly rather than continuing to operate the unit.

Q: Can I use my Daikin AC while an error code is displayed?

In most cases it is not advisable to continue operating a Daikin air conditioner while an error code is active. The code indicates that the system has detected an abnormal condition and has either shut down or entered a reduced-capacity protection mode. Continuing to force the system to operate through a fault, particularly a refrigerant pressure fault such as E4 or a compressor fault such as E5 or E6, risks accelerating damage to the compressor, which is the most expensive component in the system. Switch the unit off and arrange a diagnostic inspection before resuming normal operation.

What Do Daikin AC Error Codes Mean?

Daikin AC error codes are the system's built-in communication tool. When the unit detects an operating condition outside its acceptable range, it logs the event and displays a corresponding code on the indoor unit, wired controller, or remote display. Rather than leaving you guessing what is wrong, Daikin air conditioner error codes point directly to the component or system that needs attention.

Understanding how to read and interpret Daikin fault codes gives you a significant advantage. It tells you immediately whether the issue is something you can address at home, such as a dirty filter or a tripped circuit breaker, or whether it requires a licensed Daikin technician with refrigerant handling certification and diagnostic equipment to resolve safely.

This guide covers every major Daikin diagnostic code category, explains what each code means in plain language, outlines the likely cause and the correct fix, and tells you honestly which codes are DIY-addressable and which ones require professional attention. Whether you have a Daikin split system, a multi-head system, or a ducted reverse cycle unit, this reference covers the full range of fault indicators used across the Daikin product line in the Melbourne market.

A Daikin error code that keeps reappearing after being cleared has not been resolved. The underlying fault is still present and will continue to cause the same code to surface until the root cause is diagnosed and fixed by a certified Daikin technician. Repeated clearing without repair often leads to further component damage.

How to Read Daikin Error Codes on Your Unit

Before looking up a specific code, it helps to understand how Daikin air conditioner error codes are displayed and retrieved. The method varies slightly depending on the type of unit and controller you have, but the underlying diagnostic system is consistent across the Daikin range.

Indicator Light Flash Patterns

On Daikin split systems without a digital display, fault codes are communicated through the indicator lights on the indoor unit front panel. The operation lamp and timer lamp flash in a defined pattern. Count the number of flashes in each sequence and note the combination. For example, one flash of the operation lamp followed by four flashes of the timer lamp corresponds to a specific fault code documented in the Daikin service manual for your model. The flash pattern repeats continuously until the fault is cleared.

Wired Zone Controller Display

Daikin ducted and commercial systems typically use a wired zone controller that displays error codes alphanumerically on its screen. The code appears directly as a two-character combination such as E4 or U4, making identification straightforward. Some wired controllers also display a brief text description of the fault alongside the code. Press the inspect button on the controller to retrieve the fault code if it is not currently displayed on the main screen.

Remote Control Display

Some Daikin remote controls display a simplified fault indicator when a fault is active, though the full alphanumeric code is typically only visible on the indoor unit itself or a wired controller. If your remote shows a flashing icon or the letters CH followed by a number, this is the remote's version of a fault notification. The full diagnostic code requires inspection of the indoor unit or accessing the service mode through the wired controller.

Inverter Service Mode Fault History

Daikin inverter systems store a history of fault events that can be retrieved through a service mode accessible via the wired controller or using Daikin diagnostic equipment connected to the outdoor unit. This fault history is more detailed than the live error display and includes the fault code, the time it occurred, and any associated operating data at the time of the fault. A certified Daikin technician uses this history to identify patterns and causes that might not be obvious from the current code alone.

Indoor Unit Fault Codes

Daikin Indoor Unit Error Codes, A Series

A series Daikin error codes indicate faults that originate within or are detected by the indoor unit. These include protection events triggered by temperature limits, drain water management, and indoor unit component failures. Here is the complete A series Daikin air conditioner error codes list with causes and recommended actions.

Code	What It Means	Most Likely Cause	Action Required	DIY
A1	Indoor unit PCB fault detected	Failed or damaged indoor control board, power surge damage, or moisture ingress to PCB	Power off the unit immediately. PCB inspection and replacement by a certified Daikin technician required	No
A3	Condensate float switch activated	Blocked condensate drain pipe causing drain pan overflow, triggering the float switch safety shutdown	Check and clear the condensate drain pan. A professional drain flush and biocide treatment is required to fully resolve	Partial
A5	Freeze protection or high discharge temperature	Restricted airflow due to a clogged filter, dirty evaporator coil, or low refrigerant causing coil temperature to drop below the safe threshold	Clean the return air filter first. If the code persists after a filter clean, a coil inspection and refrigerant pressure test is required	Partial
A6	Indoor fan motor overcurrent or speed fault	Fan motor winding failure, worn capacitor, or obstruction preventing the fan from reaching its target speed	Fan motor inspection and replacement or capacitor test by a certified Daikin technician. Do not continue running the unit	No
A7	Swing flap motor fault on indoor unit	Swing flap motor failure or obstruction preventing the louver from completing its travel range	Check for physical obstructions in the swing flap path. If no obstruction is present, swing flap motor replacement by a technician is required	Partial
A9	Electronic expansion valve fault on indoor unit	Expansion valve coil failure or valve body fault affecting refrigerant flow control through the indoor unit	Expansion valve inspection and replacement by a certified Daikin technician. Refrigerant circuit pressure check also required	No

Refrigerant Circuit Fault Codes

Daikin Outdoor Unit Error Codes, E Series

E series codes in the Daikin AC fault codes system relate to pressure, electrical, and component faults primarily associated with the outdoor unit and the refrigerant circuit. These are among the most important Daikin diagnostic codes to understand because they directly affect whether the system can cool or heat and whether continued operation risks compressor damage.

Code	What It Means	Most Likely Cause	Action Required	DIY
E1	Outdoor unit PCB fault	Outdoor control board failure, power surge damage to outdoor electronics, or inverter drive fault	Outdoor unit PCB inspection and replacement by a certified Daikin technician. Do not attempt to reset repeatedly	No
E3	High pressure protection trip	Blocked outdoor condenser coil restricting heat rejection, inadequate clearance around outdoor unit, or overcharged refrigerant circuit	Check outdoor unit clearance and clean visible coil debris. If high pressure persists, refrigerant pressure test and condenser coil wash by a Daikin technician	Partial
E4	Low pressure protection trip	Refrigerant leak causing circuit pressure to drop below the safe operating threshold. The system shuts down to protect the compressor	Refrigerant leak detection, leak repair, and recharge to specification by a licensed ARCtick-certified Daikin technician. Mandatory professional repair	No
E5	Outdoor unit inverter overcurrent protection	Compressor drawing excessive current due to a mechanical issue, refrigerant circuit fault, or inverter drive failure	Inverter and compressor inspection by a certified Daikin technician. Refrigerant pressure check included in diagnosis	No
E6	Compressor startup or operation fault	Compressor failing to start under load, refrigerant circuit issue preventing normal compression, or compressor winding fault	Compressor electrical and pressure test by a certified Daikin technician. This code warrants urgent attention to avoid compressor failure	No
E7	Outdoor fan motor speed or current fault	Outdoor fan motor winding failure, worn fan motor capacitor, or fan blade obstruction preventing the motor from reaching its target speed	Outdoor fan motor inspection, capacitor test, and replacement as required by a certified Daikin technician	No
E8	Input overcurrent protection on outdoor unit	Electrical supply issue, wiring fault, or component drawing excessive current from the outdoor unit power supply	Electrical inspection of outdoor unit wiring and supply by a certified Daikin technician. Check circuit breaker and supply voltage before calling	Partial
E9	Electronic expansion valve fault on outdoor unit	Outdoor expansion valve coil or body failure affecting refrigerant flow control at the outdoor unit stage	Expansion valve inspection and replacement by a licensed Daikin technician with refrigerant circuit pressure check	No

Sensor Fault Codes

Daikin Sensor Error Codes, C and H Series

Daikin systems use thermistors and temperature sensors throughout both the indoor and outdoor units to monitor operating conditions and make real-time adjustments to compressor speed, fan speed, and expansion valve position. When a sensor produces an out-of-range reading, the corresponding C or H series Daikin aircon error code is triggered and the system may enter a protection state or reduced-capacity operation.

Code	Sensor Location	What It Affects	Action Required	DIY
C4	Indoor heat exchanger thermistor	Controls coil temperature protection, heating and cooling mode regulation	Thermistor resistance test and replacement by a certified Daikin technician in Melbourne	No
C5	Indoor heat exchanger secondary thermistor	Secondary coil temperature monitoring, affects protection thresholds in cooling and heating	Thermistor resistance test and replacement by a certified Daikin technician	No
C9	Indoor suction pipe thermistor	Monitors refrigerant suction temperature, affects expansion valve control and protection	Thermistor inspection, resistance test, and replacement as required by a Daikin technician	No
CJ	Indoor room temperature thermistor	Controls heating and cooling cycles based on room temperature, affects setpoint accuracy	Room thermistor resistance test and replacement, check for drafts or heat sources affecting the sensor reading	No
H3	Outdoor high pressure switch	High pressure circuit protection on the outdoor refrigerant circuit	Outdoor unit pressure switch inspection, refrigerant pressure test, and condenser inspection by a Daikin technician	No
H4	Outdoor low pressure switch	Low pressure circuit protection, compressor protection in low refrigerant conditions	Refrigerant pressure test and leak detection by a licensed Daikin technician. Low pressure switch replacement if required	No
H9	Outdoor air temperature thermistor	Outdoor ambient temperature reading used for heating and defrost cycle management	Outdoor thermistor resistance test and replacement by a certified Daikin technician	No
F3	Discharge pipe thermistor	Monitors compressor discharge temperature for overheating protection in both heating and cooling modes	Discharge pipe thermistor test and refrigerant circuit inspection by a Daikin authorised technician	No
F6	Refrigerant overcharge or incorrect refrigerant type detection	Refrigerant circuit pressure management across all operating modes	Refrigerant circuit pressure test and charge verification by a licensed ARCtick-certified technician	No

Communication Fault Codes

Daikin Communication Error Codes, U Series

U series codes in the Daikin error codes list indicate communication failures between system components. These are among the most disruptive fault codes because they prevent the indoor and outdoor units from coordinating and can result in a complete system shutdown even when both units are individually functional.

Code	What It Means	Most Likely Cause	Action Required	DIY
U0	Refrigerant shortage detected through inverter operation pattern	Low refrigerant level causing abnormal compressor current draw pattern that the inverter interprets as a circuit fault	Refrigerant pressure test and leak detection by a licensed Daikin technician. Circuit recharge once leak is repaired	No
U2	Instantaneous power failure or abnormal voltage detected	Power supply instability, voltage drop, or a brief power interruption that the inverter detected as abnormal	Check circuit breaker and supply voltage stability. If power supply is stable and the code persists, inverter inspection by a Daikin technician	Partial
U4	Transmission fault between indoor and outdoor units	Damaged, disconnected, or incorrectly wired communication cable between indoor and outdoor units, or a failed communication IC on either PCB	Inter-unit communication wiring inspection by a certified Daikin technician. PCB communication component test if wiring is intact	No
U5	Communication fault between indoor unit and wired remote controller	Damaged or incorrectly terminated remote controller wiring, incorrect controller configuration, or controller PCB fault	Remote controller wiring inspection and configuration check by a certified Daikin technician	No
UA	Combination error, incompatible indoor and outdoor units connected	Mismatched indoor and outdoor unit models, incorrect unit combination after a component replacement, or incorrect DIP switch configuration	Unit compatibility check and DIP switch configuration inspection by a certified Daikin technician	No
UF	Outdoor unit capacity setting fault or address conflict in multi-system	Incorrect capacity configuration after installation or replacement, or address conflict in a multi-indoor unit system	System configuration review and address correction by a certified Daikin technician	No

A U4 communication fault is one of the most common Daikin fault codes seen after an electrical storm or power surge in Melbourne. The communication cable between the indoor and outdoor units is vulnerable to voltage spikes. If a U4 code appeared following a storm, have the inter-unit wiring inspected before assuming a PCB fault.

How to Reset a Daikin AC Error Code, The Right Approach

Many homeowners ask how to reset a Daikin AC error code, and the honest answer is that a reset without addressing the underlying fault is only a temporary measure. Here is the correct reset procedure and the important caveat that goes with it.

Note the Error Code Before Resetting

Before attempting any reset, write down the exact code displayed on the indoor unit or controller. Once power is cut and restored the code may clear from the live display, and you will need the code reference to communicate accurately with a technician. Some codes also provide a sub-code that gives additional detail, so note the complete display.
Address Any Obvious Cause Before Resetting

If the code is A5 and the filter is visibly dirty, clean the filter before resetting. If the code is A3 and the drain pan is overflowing, empty it and attempt to clear the drain before resetting. If the code is E3 and the outdoor unit is surrounded by debris, clear the obstruction before resetting. Addressing the obvious contributing factor before a reset gives the reset the best chance of holding.
Perform the Reset

Turn the Daikin unit off using the remote. Go to the switchboard and switch the dedicated circuit breaker for the air conditioner to the off position. Wait a minimum of thirty seconds to allow the capacitors in the inverter to discharge. Switch the breaker back to the on position. Wait a further two minutes before attempting to restart the unit using the remote.
Monitor the System After Restart

After the reset, run the system in the appropriate mode and observe it for at least thirty minutes. If the same code reappears within this period, the underlying fault has not been resolved and a certified Daikin technician in Melbourne needs to be contacted. Do not continue cycling through repeated resets, as this can escalate component stress in the inverter and compressor.
Contact a Daikin Technician If the Code Returns

A code that returns after a reset and an obvious-cause correction confirms that a professional diagnosis is required. Share the code you noted in step one with the technician. This allows them to prepare for the specific fault type before arriving and bring any likely replacement parts, which reduces the time needed to complete the repair in a single visit.

The Daikin inverter system stores a fault history that is not erased by a simple power cycle reset. Even after the live error code clears from the display, a certified Daikin technician can retrieve the complete fault history from the inverter memory to confirm what caused the original fault and whether the same condition has occurred previously.

Daikin AC Error Code Troubleshooting, What You Can Fix and What Needs a Technician

Not every Daikin fault code requires a service call. A small number of codes are triggered by conditions that a homeowner can address safely without any tools or technical knowledge. Here is a clear breakdown of which Daikin error codes are homeowner-addressable and which ones require a licensed technician.

Codes You Can Address at Home

A5, clean the return air filter if it is visibly clogged and test the system again. If the code clears and does not return, the filter was the cause
A3, check the condensate drain pan and empty any accumulated water. A temporary measure only as the drain still needs a professional flush
A7, visually inspect the swing flap path for any physical object preventing normal movement and remove it if present
E3, check that the outdoor unit has adequate clearance on all sides and that no debris is blocking the coil face before calling a technician
U2, check the circuit breaker and attempt a reset after confirming the power supply is stable
E8, check the circuit breaker and supply voltage before calling a technician

Codes That Always Require a Licensed Technician

E4, low refrigerant requires ARCtick-licensed leak detection, leak repair, and recharge. Illegal for unlicensed persons to handle refrigerant in Australia
U4, communication wiring faults require diagnostic equipment and wiring access not available to homeowners
A1 and E1, PCB faults require component-level diagnosis and replacement by a Daikin-trained technician
E5 and E6, compressor and inverter faults involve high-voltage components and refrigerant circuit diagnosis
All C and H series sensor codes, thermistor replacement requires access to internal components and resistance measurement tools
F3 and F6, discharge pipe and refrigerant circuit codes require pressure equipment and refrigerant certification

Why Melbourne Homeowners Trust Our Daikin Technicians for Error Code Repairs

Reading a Daikin error code is the first step. Understanding its context within the system's operating history, confirming whether it reflects a genuine fault or a transient event, and resolving the root cause rather than just the symptom is what separates a lasting repair from a temporary fix. Our team works exclusively on Daikin systems and reads Daikin fault histories every day across Melbourne.

Daikin Only Specialists

Every technician works exclusively on Daikin split, multi-head, and ducted systems across the full range of models in the Melbourne market.

Full Fault History Access

We retrieve the complete inverter fault history from your unit before recommending any repair, ensuring the diagnosis is based on the system data rather than assumption.

Same-Day Service

Same-day Daikin AC fault repair in Melbourne is available for urgent error codes. Contact us early for the best chance of a technician attending the same day.

Written Quotes Always

A written quote is provided after the diagnostic inspection and before any repair work begins. You decide whether to proceed with full information.

ARCtick Licensed

All refrigerant-related error code repairs, including E4 and U0 refrigerant faults, are handled by ARCtick-licensed technicians meeting Australian legal requirements.

Daikin AC Error Code Repair and Related Services in Melbourne

Whether your Daikin split system is displaying an E4 refrigerant code, a U4 communication fault, an A1 PCB error, or any other Daikin diagnostic code, our certified technicians across all Melbourne suburbs carry the tools, the diagnostic equipment, and the genuine Daikin parts to resolve the fault accurately in a single visit.

Daikin Split System Service Melbourne

Full annual service for all Daikin wall-mounted and multi-head split systems, including inverter fault history scan, refrigerant pressure check, and error code prevention maintenance.

Learn More

Daikin Ducted System Service Melbourne

Comprehensive servicing for Daikin ducted reverse cycle systems including zone controller diagnostic checks, fault history retrieval, and full system performance confirmation.

Learn More

Daikin AC Repair Melbourne

Certified diagnosis and repair for all Daikin error codes, from E4 refrigerant faults and U4 communication errors to A1 PCB replacements and A5 airflow restorations across Melbourne.

Book a Repair

Frequently Asked Questions About Daikin AC Error Codes

These are the questions Melbourne homeowners and property managers ask most often when a Daikin air conditioner displays a fault code.

What are Daikin AC error codes and how does the system generate them?

How do I fix Daikin AC error codes at home?

How do I reset a Daikin AC error code properly?

Why does my Daikin AC keep showing the same error code after being reset?

Which Daikin error codes are the most serious and require urgent repair?

Can I use my Daikin AC while an error code is displayed?

Daikin AC Error Codes, What You Now Know

Daikin air conditioner error codes are a precise and genuinely useful diagnostic tool. Rather than leaving you with a system that simply does not work and no information about why, the Daikin fault code system tells you directly which part of the system needs attention and how urgently.

The codes covered in this guide span the full range of Daikin split system error codes and ducted system fault indicators used across the Melbourne market. Some you can address at home with a filter clean or an obstruction check. Most require a certified Daikin technician with refrigerant certification, diagnostic equipment, and access to the inverter fault history to resolve properly and permanently.

If your Daikin system is displaying a fault code that is not resolving with basic checks, contact a certified Daikin technician in Melbourne for a same-day diagnostic inspection. Our technicians read Daikin fault codes and fault histories every day across Melbourne and resolve the majority of error code faults in a single visit with the correct parts on board.

Is Your Daikin AC Showing an Error Code in Melbourne? We Can Help

Certified Daikin technicians, same-day availability across all Melbourne suburbs, full inverter fault history diagnosis, and written quotes before every repair.

Call 03 7074 1838