Daikin Air Conditioner Flashing Green Light, What It Means

A Daikin air conditioner flashing green light usually means the unit has detected a fault and stopped itself. A green light blinking on the wall unit is the moment most people reach for the phone. It looks like a warning, the room has usually stopped doing what it should, and nothing in the house explains it.

Sometimes it is a fault. Quite often it is not, and there is one very common situation where Daikin states in its own manuals that a flashing operation lamp does not indicate a malfunction at all. This page sets out what the lights on a Daikin actually mean, how to pull the error code off your own remote, and which situations are worth a technician.

What a flashing green light on a Daikin means

Here is the quick answer. Daikin wall units carry a small row of lamps under the front panel, and each one says something different.

The green operation lamp in normal use

Daikin calls the main green lamp the operation lamp. It lights when the unit starts and goes out when the unit stops, and that is the whole of its normal job.

There is one quirk worth knowing before you assume a dead lamp means a dead unit. Daikin documents a monitor brightness setting, and if that setting is turned off the operation lamp will not light even while the unit is running. So a Daikin that is clearly cooling the room with no green light showing is not broken, it has simply been dimmed.

On Zena and similar models the lamp is a coloured monitor instead, sometimes called the Daikin eye. It shows blue for cooling, red for heating, green for dry, white for fan only, and red and blue together for automatic. When a timer is set it turns orange for a few seconds and then returns to the mode colour.

The one case where a flashing green light is not a fault

This is the section worth reading before you book anything, and it applies to a lot of Melbourne homes.

If your system is a multi split, meaning several indoor units running from one outdoor unit, the indoor units cannot run in opposing modes at the same time. Daikin gives priority to whichever unit was switched on first.

When a second unit is then set to a conflicting mode, that second unit does not fail. It enters standby, and its operation lamp flashes. Daikin states plainly in its operation manuals that this does not indicate a malfunction.

What this looks like in a house. Somebody puts the lounge room on cooling in the morning. Later somebody else sets the bedroom to heating. The bedroom unit blows nothing and its green light blinks. Nothing is broken. The bedroom is waiting for the lounge room to stop or to change mode.

The fix is to set every indoor unit to the same mode, or to switch off the unit that claimed priority first. Automatic mode follows the same rule, so a unit set to automatic will keep running if it lands on cooling and will go to standby if it lands on heating while another unit is cooling.

If you have a single split, one indoor unit and one outdoor unit, this does not apply to you and a flashing operation lamp should be treated as a fault.

How to read the error code from your Daikin remote

A flashing operation lamp means a code has been stored, and you can read it yourself in under a minute. Knowing the code before you call turns a diagnostic visit into a repair visit.

The exact button varies by remote. On most Daikin wireless remotes it is the timer cancel button, on newer remotes it is marked Cancel, and on some recent models it is the clock button.

1. Point the remote at the indoor unit.
2. Hold the timer cancel button down for about five seconds. The temperature display changes to a code display and starts blinking.
3. Press the same button repeatedly. The code steps through the list one entry at a time.
4. Listen to the unit. A short beep or two quick beeps means the code shown is not yours. A long continuous beep means the code on screen is the one stored.
5. Write it down. Two characters, such as U4 or A5.
6. To exit, hold the button for about five seconds again. The display also clears itself if you leave it alone for a minute.

On some older remotes the entry is different. Pressing the temperature up, temperature down and mode buttons together enters the diagnosis, the temperature buttons change the digits, and the mode button switches between the first and second character. The beeps mean the same thing.

If the display shows 00, that is the Daikin code for normal. No fault is stored.

What the Daikin error codes mean

These are the codes a wireless remote will step through on a wall split. The list is longer on ducted and commercial systems.

What does U4 mean on a Daikin air conditioner?

U4 is the code people search for most, and it has a specific meaning. Daikin defines it as a failure of transmission between the indoor unit and the outdoor unit.

In plain terms the two halves of your system have stopped talking to each other. The indoor unit is asking for cooling or heating and getting no answer back from outside.

It is a communication fault rather than a mechanical one, which is why the indoor fan often still works while nothing useful happens to the temperature. The cause sits in the wiring between the units, in a board at either end, or in the power supply to the outdoor unit. None of those is a homeowner job, and it is one of the codes most worth reporting on the phone before anybody drives out.

Daikin behaviour that looks like a fault and is not

Before reading anything into a stopped unit, check whether it is doing one of these.

What to do before you call anyone

If the green lamp is flashing on a single split, work through this list first.

1. Check the air filters. the Daikin troubleshooting guidance for a flashing operation lamp asks this first. A blocked filter can trip a protection.
2. Check nothing is blocking the air inlet or outlet on either the indoor or the outdoor unit.
3. Read the error code from the remote using the steps above, and write it down.
4. Switch the unit off, turn off the circuit breaker, leave it off for about five minutes, then switch it back on, because the Australian manuals give no set wait time.
5. Start it again from the remote. If the operation lamp is still flashing, the fault is real and the code you wrote down is what the technician needs.

If your system is a multi split, add one step before all of that. Check what every other indoor unit in the house is set to, because a mode conflict costs nothing to fix.

When to stop and make the call

Some situations are not worth working through on your own.

• The operation lamp keeps flashing after a filter check and a full power cycle.
• The code is U0, U4, E5, E6, F3, F6 or anything in the L series. These sit in the refrigerant circuit, the compressor, the communication link or the inverter, and none is a homeowner repair.
• Water is appearing where it should not be, on the wall below the unit or dripping from the fascia.
• There is a burning smell. Stop the unit and switch it off at the breaker before anything else.
• The breaker trips every time you restore power.

Everything else on this page is something you can check from the lounge room floor.

A note on where these meanings come from

Daikin Australia does not publish a consumer page on flashing lights or error codes, which is part of why the topic is so badly covered. The meanings here are taken from Daikin operation manuals and the Daikin troubleshooting documentation for the same model families sold here.

Where Daikin publishes two different figures for the same behaviour, such as defrost duration, this page gives the range rather than picking the number that sounds best.

Getting the light to go out

A flashing green light on a Daikin is the unit telling you it has stopped and stored a reason. On a multi split it is very often just a mode disagreement between rooms. On a single split it is a code waiting to be read, and reading it yourself takes a minute and changes the conversation you have with whoever comes out.

Filters first, code second, then the call. If the code points at the compressor, the refrigerant circuit or the link between the two units, that is the point where guessing costs more than asking. We send a licensed technician who works on Daikin split, multi head and ducted systems across Melbourne, and the price is confirmed before any work starts. It is also worth knowing how often you should service your air conditioner, since a clean filter prevents several of the codes above.

If the symbols on your remote are the puzzle rather than the lights on the wall, our guide to Daikin air conditioner symbols covers those instead.

A lamp that keeps coming back is one of several signs a Daikin needs servicing without waiting, which is worth reading before the weather turns.

For the repair itself, our Daikin air conditioning service covers split, multi head and ducted systems across Melbourne. Send the code through when you request a quote and the visit starts with a diagnosis rather than a guess.