Of the 271 rated models we list, 263 deliver their nameplate capacity in the official GEMS test, so a unit blowing warm air is almost never a weak label. Here is the order a technician works through, and the four checks to do before you call.
Warm air is one symptom with about eight causes
- 1Mode and setpointyou can check
- 2Filters and airflowyou can check
- 3Drainon the visit
- 4Controller fault historyon the visit
- 5Electrical partson the visit
- 6Refrigeranton the visit
An air conditioner that runs but does not cool has a fix somewhere between a button on the remote and a new compressor, and what decides which one you get is the order the checks are done in.
On our repairs page the order is written down: mode and setpoint, filters and airflow, the drain, the fault history stored in the controller, then the electrical parts and, last, the refrigerant. Common and cheap first, expensive and rare last, and nothing replaced on a hunch.
The order matters because the expensive causes and the cheap ones produce the same air: a clogged filter, a tired capacitor and a refrigerant leak all end in a unit that hums and blows air that is not cold.
Four checks before you call
The manufacturers' own troubleshooting pages, which sit on our manuals and brochures page, agree on what to look at first.
Mitsubishi Electric's MSZ-AP and MSZ-EF manuals ask, in this order: is the temperature setting appropriate, is the fan speed set high, are the filters clean, is anything blocking the inlet or outlet of the indoor or outdoor unit, and is a window or door open.
Panasonic's Z Series instructions list the same four: set the temperature correctly, close doors and windows, clean or replace the filters, clear any obstruction at the air inlet and outlet.
In practice: put the unit in cool rather than auto, dry or fan, set it a few degrees below the room, turn the fan up from auto, and pull the filters and rinse them.
Mitsubishi Electric adds one that catches people every summer: night mode caps the fan and the compressor to keep the unit quiet, so a unit left in it feels weak all day.
And after the power has been off, or the unit has been stopped and restarted, the compressor will not run for about three minutes; the manual calls it protection from the microprocessor. Wait it out before deciding anything.
Airflow: the filter is the cause more often than the gas
A split system cools by moving room air across a cold coil. Starve it of air and the coil gets colder than it should, the moisture on it freezes, and after a while the unit is blowing thin, slightly warm air past a block of ice.
That is the frozen coil in our guide to a unit leaking water, and it starts at the filter far more often than at the refrigerant.
The outdoor unit has the same need.
Leaves packed into the coil, a fence panel a hand's width from the fan or a unit boxed into a hot side passage all reduce how much heat it can dump, and a hot outdoor coil means a warm indoor one, which is why the manuals put obstacles at the outdoor unit on the user checklist.
A yearly maintenance visit cleans both coils; when the indoor coil has gone black with mould a deep clean is the fix.
Is it just too hot outside? What the rating actually promises
The capacity on the label is measured at one condition: 35 degrees outside and 27 degrees inside, the standard test the star rating uses. We checked our own catalogue against the official GEMS registration data: of the 271 models we list with a rated cooling capacity, 263 deliver at least their nameplate kilowatts in that test.
The eight that do not are all large ducted units, and only three miss by more than half a kilowatt: Toshiba's Digital Ducted 16 kW is rated at 14 kW, Daikin's Inverter Ducted 25 kW at 23.5 kW and its Premium Ducted 25 kW at 24 kW.
Every wall split we sell meets its label. If your split is struggling, the label is not why.
Above the test point the picture changes. Mitsubishi Electric's manuals say it plainly: when the outside temperature is high, the cooling effect may not be sufficient. Western Sydney's Richmond station averages a 30.4 degree January maximum and its hot days run well past 35, so on those afternoons every unit is working beyond the condition it was rated at.
A room with west-facing glass that will not get below 26 at 4pm in a heatwave is usually a sizing question, not a repair. The calculator gives you a kW range from six questions, and the sizing guide explains what moves it.
Electrical parts and the controller history
If the checks above are clean, a technician moves to the parts that make the unit run: the capacitor that starts the compressor and fan motors, the contactor that switches them, the motors themselves. A unit that trips the breaker points here, as does one that runs for a few minutes and shuts down again.
Before any of that is tested we read the controller, because modern units store their own fault history and the repairs page puts it in one line: diagnose from the code, not the symptom.
On a Panasonic Z Series the remote has a check mode that reads the code back with a beep and a display: H97 is a locked outdoor fan motor, H98 is indoor high pressure protection, H99 is the indoor coil freeze protection, F16 is the total running current protection.
Each one narrows the visit to a part before a panel comes off. If the unit has stopped itself, note what the lights or the display are doing before you switch it off at the wall; the code is worth more to us than a description of the noise.
Refrigerant last, and never a top-up without the leak
Low refrigerant does cause warm air, and it is the cause people expect, which is why "regas" is the repair most often sold when it is not needed. A sealed system does not use its refrigerant up.
If the charge is low there is a leak, and topping it up without finding it sells you the same repair again next summer. We pressure test, trace the leak, and quote the repair before anything is fitted, which is also the work our ARC licence (AU40806) covers.
On an older system running R22 a leak is one of the cases where we quote a replacement alongside the repair, because the gas and the parts are no longer easy to get.
On a ducted system the leak can be anywhere in a pipe run through the roof; on a split system it is usually at a flare joint you can reach.
What the visit covers
The diagnosis fee is quoted when you book, and the repair is a fixed price you approve before work starts. Capacitors, sensors, contactors and consumables ride on the van, which is why most repairs finish in one visit; anything else is ordered, priced and approved before we fit it.
We repair systems we did not install, standard repairs are booked within a few business days, and if it cannot wait our 24/7 emergency repairs service jumps the queue.
When you book, tell us the brand, split or ducted, what the lights are doing, and what you have already tried from the list above; that is usually enough to arrive with the right part on the van.
Sources
- GEMS registered air conditioners dataset (E3 program), data.gov.au, CC BY 3.0: the rated cooling capacities behind the 263 of 271 figure, synced 9 June 2026
- Energy Rating, energyrating.gov.au: the test condition the rated capacity and the star rating are measured at
- Mitsubishi Electric MSZ-AP Series operating manual: the "does not cool" checklist, night mode, high outside temperature, the three minute restart
- Mitsubishi Electric MSZ-EF Series user manual: the same checklist and the restart protection
- Panasonic Z Series operating instructions: the pre-service checks, the diagnostic readout and the H and F code table
- Bureau of Meteorology climate averages, Richmond RAAF station 067105: the January maximum
- Our repairs page: the diagnosis order, the symptom table and the repair-or-replace rules quoted above