Mini Split Won’t Turn On: The Ten Second Test

By Ray Bennett · Updated 2 October 2026 · 7 min read · Checked against the maker’s manual

Mini Split Won’t Turn On: The Ten Second Test

Short answer

Lift the front flap on the head and press the small button hidden under it. If the unit starts, the machine is fine and your remote is the fault, which is usually two batteries. If nothing happens at all, it is power, and there are three places it can be switched off. Most mini splits have no reset button, so what people call a reset is really a power cycle.

A mini split that will not turn on is usually a mini split that cannot hear you. There is no wall thermostat and no switch in the hallway, so the remote is the only way most people ever talk to it, and when that goes quiet the unit looks dead when it is not.

There is one button hidden on the head itself that tells you which half of the problem you have, and it takes about ten seconds.

Before you start

What to carry: two fresh batteries, a torch and your phone. Fifteen minutes.

Gas or electric? Electric, all of it. A mini split has no gas pipe and no flue the way a furnace does, so nothing here involves a flame. Every check on this page is either power or signal.

Look at the lights on the head before you press anything. No light at all, a steady light, and a light that blinks a pattern are three completely different faults, and once you start pressing buttons you lose the evidence.

Two things to leave alone. A breaker that trips straight back. If you push it on and it snaps off again, stop there. Something is pulling a fault current, and switching it back a third time does not fix that, it just keeps feeding it: what a breaker that keeps tripping is telling you.

The isolator box on the wall by the outdoor unit. Working the switch or the pull out handle is fine and it is meant to be used. Taking the cover off is not, because the mains terminals are behind it and the unit beside it holds a charge after the power is off.

The ten second test

One press of this tells you whether you are chasing the machine or chasing the remote.

Check 1

Press the button under the flap

Lift the front flap on the head, the same panel you open to get at the filters. Along the right hand end, usually beside the display, there is one small button.

Its name depends on the brand. AUTO, MANUAL, EMER and TEST are all used, and on some it is recessed enough that you need a fingernail.

Press it once, or hold it for three seconds on a Fujitsu, which is what its manual asks for. The unit should start up on a fixed automatic setting, with no remote involved anywhere.

If it starts: the machine, the power and the board are all fine. Your fault is the remote or the signal reaching it, which is check 2.

If nothing happens at all: it is not hearing you because it has nothing to hear with. That is power, which is check 3.

Press the same button again to stop it when you are done, or pick it up on the remote once the remote is working. Left alone it will sit on that automatic setting and ignore what you actually wanted.

If the button started it, look at the remote

Check 2

Batteries, then the camera trick, then the timer

Both batteries, fresh, and the same type. Half flat batteries are worse than dead ones. They send a weak signal that works when you stand under the unit and fails from across the room, which is exactly the fault that makes people think the machine is dying.

The camera trick. Point the front of the remote at your phone camera and press a button while you watch the screen. A working remote shows a small flash of light that your eyes cannot see. If the main camera shows nothing, try the selfie camera, because a lot of rear cameras filter that light out and will tell you a good remote is dead.

The timer. A timer, a sleep setting or a weekly schedule left switched on will hold the unit off and give you no clue that it is doing it. Cancel every one of them.

Mode and temperature. Cool set to 86°F in a 72°F room has nothing to do, and neither does Heat set to 61°F. The unit is working perfectly and doing nothing.

Line of sight. Stand within the range your manual gives, about 7 metres (23 feet) on a Fujitsu, with nothing in the way, and check that bright sunlight is not falling straight onto the receiver window, which can swamp it.

Reset the remote, not the unit. Many have a pinhole marked RESET that takes a paperclip. If yours has none, take the batteries out for a minute instead.

If nothing happened, follow the power

Three places the supply can be off, and they are worth checking in this order.

Check 3Free, unless the breaker is tripping

Breaker, isolator, then the light on the head

The breaker in the panel. Look for one marked for the outdoor unit, often two switches joined together, and sometimes a separate smaller one for the head. A tripped breaker is easy to miss because it frequently sits half way rather than fully off. Push it firmly all the way off, then all the way on.

The isolator by the outdoor unit. A small box on the wall within sight of the unit, with either a switch or a pull out block. Storms, painters, gardeners and the last technician to visit all leave these off, and nothing indoors tells you about it.

The light on the head. With the breaker and the isolator both on, a head showing no light at all is a head with no supply. On a multi head system all the heads are usually fed from the outdoor unit, so one dead head with the others alive points at the wiring to that head rather than at the head itself.

What a reset really is, and what it is not

Most mini splits have no reset button anywhere on them. What people mean by resetting one is a power cycle, and the way it is usually described is too quick to work.

Switch it off at the breaker, wait five to ten minutes, then switch it back on. The wait is the part that matters, because the boards hold a charge for a while after the power goes off. Then give it another five minutes before you judge it.

The button under the flap is not a reset on most brands. Holding it down can put the unit into a forced or test mode that behaves nothing like normal running, so press it, do not hold it, unless your own manual says otherwise.

The pinhole marked RESET on a remote clears the remote and nothing else.

And if a reset does fix it but the fault comes back every few days, the reset is covering something rather than curing it. Watch for a blinking light when it next happens, because that is a code and it names the fault.

It has power and still will not do anything

The lights are on, the remote is talking to it, and it still sits there. Three ordinary reasons.

The wait. Ask for heat and the indoor fan deliberately stays off or barely turns for three to five minutes so it cannot blow cold air at you, and pressing buttons during it starts the wait again: the delay explained properly.

Another room is arguing with it. Plenty of multi head systems can only do one thing at a time, so a head asking for heat while another sits on cooling simply stops.

It is running but not doing much. That is a different guide altogether: when it runs and the room stays warm.

Questions people ask

Where exactly is the button on the head?

Under the front flap, at the right hand end, near the display. Lift the flap the whole way until it stays up and shine a torch along that edge.

Will any universal remote work with it?

Often yes, and a cheap one is a reasonable test. Set it to your brand’s code, and if it drives the unit then your original remote was the fault.

The light is blinking a pattern at me.

That is a fault code, and every maker uses its own list, so count the blinks and read them against the manual for your model. A list from another brand will send you the wrong way.

It worked yesterday and now nothing, with no storm and no power cut.

Batteries, very often. The warning is easy to miss: Fujitsu says to replace them once the remote’s range drops noticeably.

How long should I leave it off at the breaker?

Five to ten minutes. Long enough for the board to lose its charge, which is the whole point of doing it.

Only one head is dead and the rest are fine.

Then the outdoor unit and the supply are clearly alive. Try the manual button on the dead head, because that separates a dead head from a head that is simply not hearing its remote.

Sources: Fujitsu wall mounted operating manual 9315345295-03 and ASU9RL/ASU12RL operating manual 9317433099-01 (MANUAL AUTO button held 3 seconds, forced cooling after 10, remote range about 23 feet, batteries of one type, RESET button, replace batteries when the range drops, 3 minute hold after the breaker), Mitsubishi Electric service manual OBH736 for the MSZ-EF wall units (EMERGENCY OPERATION switch on the right side, stopped by the switch or the remote, residual voltage in the boards) and Gree Sapphire service manual (Auto button starts and stops the unit)