You push the button on the remote. The indoor unit beeps — so it got the signal. The fan starts. And then… nothing useful happens. Warm air, or barely cool air, or the unit just shuts off again after a minute.
Or maybe there’s no response at all. Complete silence. The unit that was working fine last summer is now just a white box on the wall.
Either way, it’s happened at the wrong time — which in Perth usually means somewhere between November and March, when the alternative to a working split system is sitting in a house that’s pushing 30°C inside by mid-morning.
Before calling anyone, it’s worth going through this list. A reasonable proportion of split system faults are things you can identify yourself — and some of them you can fix in ten minutes without any tools. The ones you can’t fix, at least you’ll know what you’re dealing with before a technician arrives.
At Air Cool Care, the split system calls we get during Perth summer follow a very predictable pattern. A large number turn out to be simple — a tripped breaker, a controller in the wrong mode, a filter so clogged the system can’t breathe. Not all of them, but enough that it’s always worth checking the basics first.
Start Here — The Checks That Take Less Than Two Minutes
What Should I Check First When My Split System Stops Working?
Before anything else, check these three things. They sound obvious. They also solve the problem more often than you’d think.
The circuit breaker. Go to your switchboard and check whether the breaker for the air conditioner has tripped. A tripped breaker usually sits visibly in a half-position between on and off — not quite either. Switch it fully off, then back on. If it trips again immediately, stop there and call a technician — there’s an electrical fault that needs professional diagnosis. If it stays on, try the unit again.
The remote controller. Dead or low batteries in the remote produce exactly the same result as a unit that’s stopped working — no response. Replace the batteries and try again. While you’re at it, confirm the mode is set to cooling (the snowflake symbol), not fan-only — fan mode will run the fan and move air around the room without doing any cooling at all. This one catches people out more than you’d expect, particularly at the start of summer when the unit hasn’t been used in months and the mode might have been left on a winter heating setting.
The isolation switch. Most split system outdoor units have a dedicated isolation switch mounted on the external wall nearby — it looks like a power point or a small switch box. Check it’s in the on position. These occasionally get knocked off accidentally.
If all three check out and the unit is still not responding or not cooling, keep reading.
Problem 1 — The Unit Turns On But Isn’t Cooling
Why Is My Split System Running But Not Producing Cold Air?
This is the most common complaint we hear in Perth during summer — the indoor unit is clearly on, air is coming out, but it’s not cold. Several things can cause this, roughly in order of how often we actually see them.
Clogged filter. Start here. A heavily blocked filter reduces airflow across the evaporator coil so dramatically that the system simply cannot cool effectively — even though it appears to be running normally. In Perth’s summer conditions, particularly in dusty eastern and northern suburbs, filters clog faster than most homeowners expect. Remove the filter panel from your indoor unit, slide the filters out, and hold them up to the light. If you can’t see through them clearly, they need cleaning. Wash with warm water, dry completely, reinstall. This alone solves the problem in a significant proportion of cases.
The outdoor unit is blocked or dirty. Go outside and look at your outdoor condenser unit. Clear any leaves, seed pods, or debris from around it — there should be at least 50cm of clear space on all sides. Check whether the fins (the thin metal slats) look heavily clogged with dust or dirt. In Perth’s summer heat, a condenser unit that can’t reject heat to the outdoor air simply cannot cool the indoor space properly. A gentle rinse with a garden hose — not a pressure washer — can help with surface dust. For Coogee, Cottesloe, Scarborough, and other coastal suburbs, check for white powdery residue on the fins — this is salt corrosion, and it reduces heat transfer.
The system has been running with the doors and windows open. An open-plan Perth home with doors and windows open on a 40°C day is asking the split system to cool the entire neighbourhood. Close everything before judging whether the system is actually underperforming.
Low refrigerant. If the filter is clean, the outdoor unit is clear, and the system is still producing barely-cool air after 20 minutes of operation, low refrigerant is worth considering. Signs include the system running continuously without reaching set temperature, ice forming on the refrigerant lines or indoor unit, and occasionally a faint chemical smell. This requires a licensed technician — refrigerant handling in Australia is legally restricted to ARCtick-certified professionals.
Problem 2 — The Unit Turns On Then Shuts Off After a Few Minutes
Why Does My Split System Keep Turning Itself Off?
A system that starts but shuts down quickly — or cycles on and off repeatedly in short bursts — is experiencing what’s called short cycling. There are a few reasons this happens.
Overheating from a blocked outdoor unit. If the outdoor condenser can’t reject heat efficiently — because it’s blocked with debris, the fins are dirty, or it’s been installed in a spot with poor airflow — the system’s safety protection shuts it down to prevent damage. Clear the area around the outdoor unit and see if the behaviour improves.
Dirty filter causing coil freeze. A clogged filter leads to reduced airflow, which leads to the evaporator coil dropping below freezing temperature, which leads to ice forming on the coil. Once the coil ices over, the system detects a problem and shuts down. Switch the system off, clean the filter, and allow any ice to fully melt — this can take a couple of hours — before restarting.
The system is oversized for the space. This one doesn’t get discussed much, but a split system that’s too large for the room will cool the space quickly, detect that the set temperature has been reached, shut off — and then the room warms up again a few minutes later, and the cycle repeats. This is a design issue rather than a fault, and the fix is either zoning the space differently or consulting with an HVAC professional.
Faulty temperature sensor. If the sensor that reads the room temperature is giving incorrect readings, the system may believe the target temperature has been reached and switch off prematurely. This requires professional diagnosis.
Problem 3 — The Unit Makes Unusual Noises
What Do Strange Sounds From a Split System Mean?
Not all noises indicate a serious problem — but some do, and knowing the difference saves you from either ignoring something that needs attention or panicking about something that doesn’t.
Rattling or vibrating. Usually indicates something has come loose — a panel, a screw, or debris inside the unit. Check that the front cover of the indoor unit is properly seated. For the outdoor unit, check for debris in the fan housing. A loose outdoor unit on its mounting brackets can also vibrate against the wall — this is usually fixable with a tighten of the mounting bolts.
Clicking sounds on startup or shutdown. Normal. The plastic casing of the indoor unit expands and contracts with temperature changes, producing a clicking or creaking sound when the system starts and stops. This is not a fault.
Grinding or squealing. This is the one to pay attention to. Grinding from the outdoor unit typically indicates bearing wear in the fan motor — this gets worse over time and eventually leads to motor failure. Don’t ignore it. Squealing can indicate the same. Book a service.
Gurgling or bubbling. Usually points to refrigerant issues — either low refrigerant or a restriction in the refrigerant circuit. Combined with reduced cooling, this is a professional repair job.
Grinding from the outdoor unit is the sound we hear about most often after a Perth summer — particularly from older systems that have been running hard for months. The bearing wear that produces that sound tends to accelerate during sustained high-load periods. Catching it in autumn, after summer, costs a fraction of what a motor replacement mid-January costs — and avoids the wait time for parts in peak season.
Problem 4 — Water Is Dripping From the Indoor Unit
Why Is My Split System Leaking Water Inside?
Some moisture around a split system during heavy cooling use is normal — but water actively dripping from the indoor unit onto the wall or floor is not. It almost always means the condensate drain is blocked.
As your split system cools the air, moisture condenses on the evaporator coil and drips into a drain pan, then exits through a drain line. If that line is blocked — commonly by dust, algae, or biological growth — the drain pan overflows and water finds another exit route, which is usually down your wall.
The fix involves clearing the drain line. A partial blockage can sometimes be resolved by carefully flushing it with warm water. A significant blockage, or one that’s already caused water damage, warrants professional attention to clear the line properly and check for any damage to the drain pan.
In Perth homes where the AC runs intensively through a long summer, condensate lines can develop blockages relatively quickly — the combination of dust, heat, and moisture creates good conditions for biological growth inside drain lines.
Problem 5 — The Unit Won’t Turn On At All
Why Is My Split System Completely Dead?
Complete non-response — no beep, no lights, nothing — after confirming the remote batteries are fine and the circuit breaker hasn’t tripped usually points to one of a few things.
Check the outdoor unit’s isolation switch (covered above). If that’s fine, check whether the outdoor unit is making any sound or showing any indicator lights. Some systems have error code displays on the outdoor unit that give you specific fault information.
If there’s genuinely no response anywhere in the system, it’s a wiring, control board, or power supply issue — all of which need professional diagnosis. Don’t attempt to investigate electrical components yourself.
When we attend a split system call-out in Perth, the first thing we do is go through the basics — power, filter, outdoor unit condition, mode setting — before assuming anything more serious. We’ll tell you honestly what we find. If it’s something simple you could have fixed yourself, we’ll show you how to check it next time. If it needs a repair, we’ll explain exactly what and why.
When to Call a Professional — and When to Wait
Which Split System Problems Need a Technician?
DIY appropriate:
- Circuit breaker reset (if it holds)
- Remote battery replacement
- Filter cleaning
- Outdoor unit debris clearance
- Minor condensate drain flush
Call a technician:
- Circuit breaker that keeps tripping
- Refrigerant leak symptoms (ice, chemical smell, consistently poor cooling)
- Grinding, squealing, or persistent unusual sounds
- Water damage from blocked drain
- Complete electrical non-response
- Error codes on the unit display
Conclusion
Most split system problems in Perth fall into a handful of categories — and most of them have a clear cause once you know what to look for. Start with the easy checks: power, mode, filter, outdoor unit. These solve the problem more often than most homeowners expect.
The ones that don’t resolve that way — refrigerant issues, electrical faults, bearing wear, significant drain blockages — need professional attention. Catching them before peak summer demand means faster service, better parts availability, and no sitting in a hot house waiting for an appointment.
Air Cool Care services split systems across Perth — from the coastal western suburbs to the eastern corridor, from Joondalup to Rockingham, and through the hills. If your system isn’t working and the basics haven’t fixed it, contact Air Cool Care today for a diagnosis based on what we actually find.