Daikin Error Codes and What They Mean

Daikin air conditioner error codes appear on the remote or as flashing lamps when the unit detects a fault. Your Daikin air conditioner has stopped doing what you asked it to do, and instead of cool air you have a letter and a number blinking at you. It might be on the wall controller, it might be a light flashing on the indoor unit, and either way it is not obvious what you are supposed to do about it.

That code is not a fault in itself. It is the unit telling you which part of the system it thinks has a problem, which is far more useful than a machine that simply stops.

This guide explains how Daikin error codes are structured, what the common ones mean, which ones you can safely act on at home, and which ones need a licensed technician. By the end you will know whether you are looking at a blocked filter or a sealed system fault.

How a Daikin air conditioner shows you an error code

Daikin systems report faults in a few different ways depending on the model and the controller you have. Knowing where to look is the first step.

• Wall mounted controllers usually display the code directly on the screen, often with a spanner or warning symbol beside it.
• Wireless remote controls on split systems normally show the code when you hold the cancel or inspection button for around five seconds.
• On wall splits the operation lamp blinks to show a fault has been stored, and the code itself is read from the remote.
• Ducted controllers and touchscreen controllers tend to show a short message alongside the code.

If you cannot find the code, the operation manual for your specific model will tell you which button reveals it. Manuals are model specific, so the one for your unit is always the definitive source.

Why your Daikin shows a code instead of just stopping

Modern Daikin systems run continuous self diagnosis. Sensors across the indoor unit, the outdoor unit and the refrigerant circuit report back constantly, and when a reading falls outside its safe range the system stops and records what it saw.

This protects the expensive parts. A compressor asked to run with low refrigerant or a blocked coil will destroy itself in a matter of hours, so the control board would rather shut down and show you a code.

That is worth remembering when a unit stops on a hot day. The shutdown is the system protecting itself, not the system breaking.

Reading the letter before you read the number

Daikin codes are two characters. The letter tells you roughly where the problem is, and the number narrows it down.

• Codes beginning with A or C point at the indoor unit.
• Codes beginning with E, F, H, J, L or P point at the outdoor unit.
• Codes beginning with U point at the system as a whole, usually power supply, communication or refrigerant volume.

That single rule does most of the work. If you see a U code, the problem is rarely inside the indoor unit, so there is no point pulling filters out. If the system is not showing a code at all and simply will not start, our guide to a Daikin air conditioner not turning on works through that instead.

Daikin error codes on the indoor unit

These are the codes you are most likely to be able to do something about, because they often relate to airflow, drainage or a sensor you can reach.

• A0 means an external protection device has activated.
• A1 means a fault has been detected in the indoor printed circuit board.
• A3 and AF both indicate a high water level in the drain tray, which usually means drainage has backed up.
• A5 means high pressure control in heating, or freeze protection in cooling, and it very often follows restricted airflow.
• A6 means the indoor fan motor has failed or is being obstructed.
• A7 means the louvre motor that swings the vanes has failed.
• A9 means an electronic expansion valve fault.
• C4, C5, C9 and CA are all sensor faults, covering the indoor coil, the suction pipe, the return air and the discharge air in that order.
• C6 means the fan motor driver has failed.

A5 deserves a note of its own because it is common and it is often misread as a serious fault. In cooling mode it usually means the indoor coil has started to ice up, and the most frequent cause of that is a filter nobody has cleaned for a season.

Daikin error codes on the outdoor unit

Outdoor codes cover the compressor, the refrigerant circuit, the inverter and the outdoor fan. Almost all of them need a technician, because almost all of them sit behind a sealed system or live electrical components.

• E1 means a fault in the outdoor printed circuit board.
• E3 means high pressure has been detected, and E4 means low pressure.
• E5 relates to the inverter compressor, either locked or running too hot.
• E7 means an outdoor fan motor failure.
• E9 means an electronic expansion valve motor fault.
• EA means a fault in the four way valve that switches the system between heating and cooling.
• F3 means the discharge temperature has climbed too high.
• F6 relates to high pressure in cooling and can indicate an overcharged system.
• H3 and H4 refer to the high pressure switch and the low pressure switch.
• H6, H7 and H8 cover compressor position, fan motor signal and compressor input.
• H9 means the outdoor ambient sensor has failed.
• J codes across the range are sensor failures, covering pressure, current, discharge pipe, suction pipe, coil and liquid pipe sensors.
• L codes relate to the inverter, including inverter board faults, high temperatures in the electrical box, over current and start up failure.
• P1 means the power supply is unbalanced, and P3 and P4 relate to electrical box temperature and the radiating fin sensor.

If you see an E, F, H, J, L or P code, stop there. There is nothing safe or useful you can do at the outdoor unit beyond clearing leaves away from it.

Daikin system and communication codes

The U group is the one homeowners notice most, partly because U0 and U4 appear so often.

• U0 means a shortage of refrigerant.
• U1 means a reverse or missing phase in the power supply.
• U2 means a power supply fault.
• U3 means a check operation has not been carried out, which usually appears after installation or service work.
• U4 means communication has failed between the indoor and outdoor units.
• U5 means communication has failed between the remote controller and the board.
• U7 and U8 cover communication between outdoor boards and between remote controllers.
• UA means an improper combination of indoor and outdoor units, or an incorrect field setting.
• UF means a wiring or piping mismatch.
• UH indicates a wider system malfunction.

U0 is worth understanding properly. Refrigerant is not consumed the way fuel is, so a genuine shortage means it has escaped somewhere. Topping the system up without finding the leak means you will be back in the same position within a season.

What is a common Daikin error code?

Across Melbourne homes the codes that come up most often are U4, U0 and A5, and each has a very different cause.

U4 is a communication failure, which frequently comes down to wiring, moisture in a terminal block or a board that has taken a hit during a storm. It appears suddenly and it usually has nothing to do with how the unit has been used.

U0 is refrigerant related and tends to build slowly over years. A5 is usually airflow, which means it is usually maintenance.

Which Daikin error codes can you clear yourself?

A small number of codes respond to things you can do safely without tools or training. It is worth trying these before you book anyone.

1. Turn the system off at the isolator or the circuit breaker, leave it off for about five minutes, then switch it back on. This clears codes triggered by a momentary event such as a power dip.
2. Remove and wash the indoor filters, let them dry completely, and refit them. This addresses a large share of A5 and freeze related codes.
3. Check the outdoor unit is clear. Leaves, garden growth and anything stacked against it restrict airflow and can trigger pressure codes.
4. Check the condensate drain outlet is running freely, which is relevant to A3 and AF.
5. Confirm nothing is blocking the indoor unit, including furniture, curtains and anything placed on top of a ducted return air grille.

If the code clears after one of those and does not return, the fault was real but minor. If it returns within a day or two, treat it as a fault that needs diagnosis.

Which Daikin faults should you never attempt yourself?

Anything involving refrigerant, the compressor, the inverter or the sealed circuit is licensed work in Australia, and for good reason.

• Refrigerant is under pressure and handling it without a licence is unlawful as well as dangerous.
• Inverter boards hold a charge after the power is switched off.
• Opening the outdoor unit exposes live terminals and a fan that can start without warning.
• Incorrect field settings can leave a system running in a way that shortens its life without showing any obvious symptom.

The practical rule is simple. If the fix requires opening a sealed part of the system or touching wiring, it is not a homeowner job.

How to clear a Daikin error code once the fault is fixed

Most Daikin systems clear a stored code once the underlying condition is resolved and the unit is restarted. On wall controllers there is often a reset or cancel function that clears the stored history.

Clearing the code is not the same as fixing the fault. A code that has been cleared but not resolved will reappear the next time the system runs under load, which in summer can be within minutes.

If a technician has attended, ask them to note the code and what they found. That record is genuinely useful the next time something goes wrong.

What if the same code keeps coming back?

A repeating code tells you more than a one off code does. It means the condition that triggered it is still present and the system is meeting it every time it runs.

Repeating pressure or freeze codes usually point to airflow or refrigerant charge. Repeating communication codes usually point to wiring or a board. Repeating sensor codes usually mean the sensor really has failed rather than drifted.

Write down the code, the date it appeared and what the system was doing at the time. Three of those entries will tell a technician more than an hour of testing.

Does an error code mean the air conditioner needs replacing?

Usually not. Sensors, fan motors, drain pumps and control boards are all replaceable parts, and a code that identifies one of them is pointing at a repair rather than a replacement.

The picture changes when the fault is in the compressor or the sealed system on an older unit. At that point the cost of the repair starts to approach the cost of a new system, and the sensible question becomes how many seasons the rest of the unit has left.

A code on its own never answers that question. What answers it is the age of the unit, its service history and which part has failed.

What to have ready before you call a technician

A short amount of preparation makes the visit faster and the diagnosis more accurate.

• The exact code, written down rather than remembered.
• The model number from the indoor unit and from the outdoor unit.
• Roughly how old the system is and when it was last serviced.
• What the unit was doing when the code appeared, including the mode it was in and the temperature it was set to.
• Whether the code clears on a restart and how long it takes to come back.

That last point is the one most people miss, and it is often the most diagnostic thing you can offer.

Keeping error codes from appearing in the first place

Most of the codes a homeowner will ever see are preventable, because most of them trace back to airflow, drainage or a system that has been running with a slow refrigerant leak.

• Wash the indoor filters regularly through the cooling season rather than once a year.
• Keep the outdoor unit clear on all sides and above.
• Have the condensate drain checked before summer rather than after it blocks.
• Book a professional service annually so that a slow leak or a tired capacitor is found while the weather is still mild.

Annual servicing is not a guarantee against faults. It is the difference between finding a problem in October and discovering it on the first forty degree day in January.

The short version

A Daikin error code is a starting point, not a verdict. The letter tells you where to look, the number tells you what the system saw, and between them you can usually tell within a minute whether you are dealing with a filter or a compressor.

Codes beginning with A or C sit in the indoor unit and are the ones most likely to respond to cleaning and airflow. Codes beginning with E, F, H, J, L or P sit in the outdoor unit and need a licensed technician. Codes beginning with U cover power, communication and refrigerant, and U0 in particular should always prompt a leak search rather than a top up.

If the code has come back more than once, or if it sits in the outdoor unit, the next step is a proper diagnosis rather than another reset. Have the code and the model numbers ready and the visit will be shorter for everyone.

Several of these codes are prevented rather than fixed, and our guide on how often to service an air conditioner in Melbourne sets out the interval.

For your model’s manual and warranty details, see the official Daikin Australia website.

Need a technician for your Daikin system? Read about our Daikin air conditioner service in Melbourne, or call 03 9088 4796.

Reviewed by AC repair and service specialist on 22 October 2026. How we write our articles