Daikin Air Conditioner Not Turning On, What to Check

You press the button on the remote, the room stays warm, and the Daikin air conditioner is not turning on at all. There is no hum from the outdoor unit, no movement from the louvre, and no sign that anything has heard you.

A system that does nothing feels worse than a system that makes a noise, because there is no clue to work with. In practice, a Daikin that refuses to start is usually stopped by something simple, and only sometimes by something expensive.

This guide works through the causes in the order a technician would check them, starting with the remote in your hand and finishing with the faults that need a licence to touch. By the end you will know whether you are looking at a flat battery, a tripped safety switch, or a control board that has failed.

Start by deciding what kind of nothing you have

Not all silence is the same, and the difference matters. Before you touch anything, look at the indoor unit and note what you can see.

• No lights at all on the indoor unit usually points at power, either at the switchboard or at the isolator.
• A light on but nothing happening usually points at a setting, a delay, or a signal that is not reaching the unit.
• A light flashing usually means the system has recorded a fault and has stopped on purpose.
• The indoor unit running while the outdoor unit stays quiet points at the outdoor side, which is a different problem again.

Those four observations narrow the field enormously. Everything that follows is organised around them.

Check the remote before you blame the machine

A surprising share of calls about a Daikin air conditioner not turning on end at the remote control. It is worth two minutes of your time before anything else.

1. Replace the batteries with a fresh pair rather than testing the old ones.
2. Point the remote at the indoor unit from about a metre away with nothing in between.
3. Watch the screen when you press the on button, because a remote with dying batteries often lights up but sends nothing.
4. Listen for the beep from the indoor unit, which confirms the signal arrived.

If there is no beep, the unit is not receiving the command. Strong afternoon sun falling directly on the receiver can also swamp the signal, which is why a system sometimes seems to work in the morning and not at four in the afternoon.

Most Daikin indoor units also carry a small manual button behind the front panel. Pressing it starts the unit in an automatic mode without the remote, and if the unit starts that way, the fault is in the remote and not in the air conditioner.

Why a Daikin will not start for the first three minutes

This one catches people out constantly, and it is not a fault. Daikin states that the air conditioner does not operate for three minutes when it is switched on immediately after being shut down, or when the operation mode is changed on the remote.

The delay exists to reduce the load on the compressor when it restarts. Starting a compressor against pressure that has not yet equalised is one of the fastest ways to shorten its life, so the control board simply waits.

If you have been pressing the button repeatedly, you may be resetting that three minute timer each time. Set the unit to cool, set the temperature well below room temperature, then leave it alone and watch the clock.

Power is a common reason for a Daikin air conditioner not turning on

When the indoor unit shows no lights whatsoever, the system is almost certainly not being fed. There are usually three separate points where the supply can be interrupted.

• The circuit breaker in the switchboard, which is normally labelled for the air conditioner.
• The safety switch or residual current device covering that circuit.
• The isolator switch mounted on the wall beside the outdoor unit.

Check all three. A breaker that has tripped will sit between the on and off positions rather than fully off, so push it firmly off first and then on.

If the breaker trips again immediately, stop. A circuit that trips the moment it is energised is telling you there is a fault drawing current it should not, and repeatedly resetting it is both unsafe and pointless.

The isolator switch nobody remembers

The isolator is a small weatherproof switch near the outdoor unit, fitted so a technician can cut power safely. It gets knocked off by gardeners, by people cleaning gutters, and by anyone tidying the side of the house over winter.

Because it sits outside and out of sight, it is often the last thing checked and the first thing that was wrong. If your Daikin worked in March and does nothing in November, look there before anything else.

Settings that quietly stop a Daikin from running

A unit that lights up and beeps but produces no cooling may be doing exactly what it was told. Run through the settings on the remote carefully.

• The mode may be set to fan only or dry, neither of which will cool the room the way you expect.
• The set temperature may be above the room temperature, so the system has no reason to start.
• A timer may be active, holding the unit off until a set hour.
• On a ducted system, every zone may be closed, which some controllers treat as a reason to stop.
• A weekly schedule left over from a previous season may be overriding the button you just pressed.

Clear any timer, set the mode to cool, drop the temperature several degrees below the room, and set the fan to high. If the unit starts, the fault was in the programming and not in the hardware.

What a flashing operation lamp is telling you

A flashing lamp is the system refusing to run rather than failing to run. It has detected something outside a safe range and has stopped itself deliberately.

On most Daikin split systems you can read the stored code by holding the cancel or inspection button on the remote for around five seconds. The display then cycles through codes until the unit beeps to confirm the one it has recorded.

The letter at the front of the code tells you where to look. Codes starting with A or C sit in the indoor unit, codes starting with E, F, H, J, L or P sit in the outdoor unit, and codes starting with U cover the system as a whole, which usually means power, communication or refrigerant volume. Our guide to Daikin error codes and what they mean covers each of them in detail.

Codes you are most likely to see on a unit that will not start

A few codes turn up again and again on systems that refuse to run at all, and knowing them saves a lot of guessing.

• U0 indicates a shortage of refrigerant, which the system treats as a reason to stop rather than run dry.
• U2 indicates a power supply voltage problem.
• U4 indicates a communication failure between the indoor and outdoor units.
• A1 indicates a fault in the indoor printed circuit board.
• A6 indicates the indoor fan motor has failed or is obstructed.
• E5 indicates the compressor has stopped on an overload protection.

U4 is worth singling out. The two halves of the system talk to each other over the interconnecting cable, and when that conversation stops, neither half will run. Rodents chewing cable, water in a junction, and a loose terminal after building work are all common reasons.

When the indoor unit runs but the outdoor unit stays silent

This is a different fault from a dead system and it narrows things considerably. The indoor unit has power and has accepted the command, so the break is further along.

• The outdoor isolator may be off while the indoor unit is fed from a separate circuit.
• The outdoor fan or compressor capacitor may have failed, which is a common wear item.
• The contactor that switches the compressor may have failed to pull in.
• The system may be in the three minute protection delay described earlier.
• A low refrigerant charge may be holding the compressor off on a pressure switch.

Only the first and the last of those are things a homeowner can sensibly assess, and even the last one only by noticing that cooling has been getting steadily weaker for weeks.

Ducted Daikin systems that will not turn on

Ducted systems add a controller, a fan coil in the roof space, and often a separate power point, so there are more places for the chain to break.

• The wall controller may have lost power while the fan coil still has it, leaving a blank screen and a working system nobody can command.
• The fan coil in the roof usually has its own isolator or power point, which can be switched off during roof work.
• A blank controller with no backlight almost always means supply, not a controller failure.
• Some controllers lock out after a fault and need the power cycled at the switchboard before they will respond.

If the controller is completely dark, start at the switchboard and at the roof space supply rather than replacing the controller.

Can a dirty filter stop a Daikin from turning on?

Not directly, but it can absolutely stop one from staying on. Restricted airflow across the indoor coil lets the coil temperature fall until the system shuts down to protect itself, and that shutdown is what most people notice.

The pattern is distinctive. The unit starts, runs for a while, then stops and will not restart for some time. If that matches what you are seeing, pull the filters out and look at them before calling anyone.

Cleaning filters every few weeks through summer is the single cheapest thing you can do for a Daikin, and it prevents a whole family of faults that look far more serious than they are. Our guide to how often you should service your air conditioner covers what else is worth doing each season.

How to reset a Daikin air conditioner properly

A reset clears a latched fault and lets the system try again. It does not repair anything, so if the same fault returns, the reset has done its job by telling you the problem is real.

1. Turn the unit off at the remote and wait for the indoor fan to stop.
2. Switch off the circuit breaker at the switchboard.
3. Leave it off for several minutes so the control boards fully discharge.
4. Switch the breaker back on and wait for the indoor unit to show a standby light.
5. Start the unit from the remote in cool mode and give it the full three minutes.

Resetting a system more than once for the same fault is a warning sign rather than a fix. A fault that keeps returning is a fault that is still there. There is a longer walk through in our guide on how to reset common air conditioning faults yourself.

What you can safely check yourself

There is a clear line between sensible homeowner checks and work that requires a licence. Everything in this list is on the safe side of it.

• Remote batteries, signal path and the manual start button on the indoor unit.
• Circuit breaker, safety switch and outdoor isolator positions.
• Mode, set temperature, fan speed, timers and schedules.
• Return air filters and any visible blockage at the outdoor unit.
• Reading the stored error code from the remote so you can describe it accurately.

Doing those five things before you call means the technician arrives already knowing a great deal, which usually shortens the visit.

What needs a licensed technician

Anything past the switch positions and the settings involves live electrical parts, sealed refrigerant, or both. In Australia, work on the refrigerant circuit requires a licence, and so does most of the electrical work inside these units.

• Capacitors, contactors, relays and control boards.
• Any measurement of refrigerant pressure or charge.
• Compressor and inverter faults.
• Interconnecting cable repairs between indoor and outdoor units.
• Any circuit that trips the breaker as soon as it is switched on.

A capacitor can hold a dangerous charge long after the power is off, which is the main reason the cover on an outdoor unit is not a homeowner job.

How a technician diagnoses a Daikin that will not start

Knowing the sequence helps you understand what you are paying for, and it also tells you which observations are worth passing on when you call.

1. Confirm supply at the isolator and at the indoor unit terminals.
2. Read the stored fault code from the controller or the unit itself.
3. Check communication between the indoor and outdoor boards.
4. Test the capacitor, contactor and fan motor on the outdoor unit.
5. Measure refrigerant pressures if the fault points at the sealed system.
6. Check sensor resistances against the values in the service data.

That order is deliberate. It moves from cheap and fast to slow and expensive, so the simple causes are eliminated before anyone opens the refrigerant circuit.

Why is my Daikin air conditioner not turning on but the light is on?

A standby light with no operation means the unit has power and has not started. That usually points at the remote signal, at a setting such as mode or temperature, at an active timer, or at the three minute restart delay.

Try the manual start button on the indoor unit. If the system runs from that button, the air conditioner is fine and the command was never arriving.

How long should a Daikin take to start cooling?

Allow three minutes for the protection delay, then a further few minutes before the air coming out feels properly cold. A system that blows air at room temperature for twenty minutes has a genuine problem rather than a slow start.

On a very hot day the first run of the afternoon always takes longer, because the whole house and the ductwork have to give up their heat before the room temperature moves. A system that starts but never gets the room down is a different fault, and our guide to a Daikin air conditioner not cooling deals with that one.

When a Daikin that will not start is telling you something bigger

Age matters. A system that has needed several resets across a season, or that has thrown refrigerant shortage codes more than once, is usually approaching the end of its working life rather than having a run of bad luck.

Refrigerant does not get used up. If a system is short of it, there is a leak, and the repeated top ups people sometimes pay for are treating a symptom.

That is the point at which it is worth comparing the cost of the next repair against the cost of replacement, rather than fixing the same fault a third time. We have set out how to weigh that up in our guide on whether it is worth repairing an old air conditioner.

Getting it running again

Most Daikin systems that will not turn on are stopped by a battery, a switch, a setting or a protection delay, and those four account for a large share of call outs that end without any parts being fitted. Working through them in order costs you nothing and often solves the problem in a few minutes.

If you have checked the remote, the breakers, the isolator and the settings and the system still refuses to start, or if it has recorded a fault code, the next step needs test equipment and a licence.

We send a licensed technician who works across Melbourne on Daikin split, multi head and ducted systems, and we confirm the price with you before any work starts. If your system has stopped and you would rather not spend the afternoon on it, we are happy to take a look.

If the unit is old enough that replacement is worth considering, our comparison of Daikin and Mitsubishi air conditioners is a useful starting point.

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