Start with the 30-second settings check
Before you touch a filter or grab the hose, rule out the simple stuff — plenty of "broken" aircons are just set wrong:
- It's on Cool, not Fan or Dry. Fan just blows air around without cooling it. Dry pulls humidity but barely cools. Look for the snowflake symbol on the remote.
- The temperature is set low enough. If it's set to 25 and the room's already 25, the unit thinks it's done. Drop it a few degrees and give it ten minutes.
- The remote batteries aren't flat. A weak remote can fail to send the setting without any obvious sign. Fresh batteries cost nothing to rule out.
If the settings are right and it's still blowing room-temperature air, work through the list below in order — airflow first, because that's nearly always it.
The real reasons it won't cool, in the order to check
1. A dirty filter — the most common, and the easiest fix
This is the one we see more than any other. A clogged filter starves the indoor unit of airflow, so the cold air it makes can't get out into the room. The unit runs and runs, the room never cools, and your power bill climbs for nothing.
How to spot it: pop the front cover off the indoor unit and look at the mesh filters. If they're grey, furry or you can't see through them, that's your airflow gone.
DIY fix (about 10 minutes): slide the filters out, vacuum the loose dust off, then rinse them under the tap with a little mild soap. Let them dry fully, refit, and run it. If the cold comes back, that was the whole problem.
2. A dust-clogged outdoor unit — the big North Queensland one
This is the cause most people never think to check, and up here in the dry tropics it's a real one. The outdoor unit is how your aircon gets rid of the heat it pulls out of your house — it dumps it into the outside air through a coil and a set of thin metal fins. Townsville and Mackay are dry and dusty for most of the year, and over a season those fins pack solid with dust, grass clippings, lawn-mower throw and grime. Once the outdoor unit can't breathe, it can't get rid of the heat — so no matter how hard the inside works, the air never goes properly cold.
How to spot it: go and look at the outdoor box on the wall or the ground outside. If the fins are caked grey, full of leaves and lint, or sitting against a fence or in a garden bed with no air around it, that's a unit that's choking.
DIY fix: switch the aircon off at the wall first. Clear the leaves, grass and rubbish off and around it, then gently hose the fins from the outside in to flush the dust out — a normal garden hose, not a pressure washer (high pressure bends the fins and makes it worse). Let it dry, switch it back on, and see if the cold returns. Don't pull the unit apart or touch the electrical side — the cabinet stays on.
3. An iced-up indoor coil
If the indoor unit has frozen over, you'll get little or no cold air, often with water dripping once it starts to melt. A choked filter or a low gas charge is usually behind it.
How to spot it: turn the unit off, open the front cover, and look for white ice or frost on the coil behind the filters.
DIY fix: leave it switched off for a few hours to thaw fully, then run it on Fan mode for half an hour to dry out. Clean the filter while you wait. If it cools fine after that and stays clear, the dirty filter was the cause. If it ices up again, that points to low refrigerant — and that's a tech job. (If it's leaking water, our dripping-water guide walks through that side of it.)
4. Low refrigerant — a gas leak
Refrigerant is the gas that does the actual cooling. It's meant to stay sealed in the system forever — if it's low, the system has a leak somewhere, and topping it up without finding the leak just buys a few weeks. This is not a DIY job and not a cleaning job: handling refrigerant in Australia legally requires a licensed tech.
The tell-tale signs: the unit only blows cold for a little while then goes warm; ice forming on the indoor unit or on the thin copper pipe outside; a faint hissing or bubbling sound. If you're seeing those andthe filter and outdoor unit are already clean, stop checking and book a tech.
5. An old or undersized unit working too hard
In a North Queensland summer, a tired ten-or-fifteen-year-old unit — or one that was always a bit small for the room — can simply run out of puff on the hottest days. It'll cool a little, but never get the room down the way it used to. A clean and a service can claw back some performance, but past a certain age the honest answer is that the unit's near the end of its life.
When it's airflow, a clean brings the cold back
Most weak-cooling jobs up here are dirt — a choked filter and a dust-packed coil. We take the cover off and clean what a quick wipe can't reach, inside and out. The Standard Clean is from $89/unit (filter clean, coil rinse, drain check, system test, outdoor unit checked). For a unit that's really loaded up, the Premium Deep Clean is $189/unit — the full chemical wash with the barrel pulled out. When dirt was the cause, the cooling comes back. No call-out fee, and you pay after the clean.
When it's a tech, not a clean
A clean fixes the airflow problems — the filter and the coil. It can't make gas appear in a leaking system or add years to a worn-out unit. Call a licensed tech instead of booking a clean when:
- The filter's clean and the outdoor unit's clear, and it still won't cool.
- It only blows cold for a short while, then drifts back to warm.
- You can see ice on the indoor unit or on the copper pipe outside.
- There's a hissing or bubbling sound while it runs.
- The unit's well over ten years old and was always a struggle on hot days.
The honest answer
Most of the time, an aircon that won't cool is simply choked with dust — a blocked filter inside or a packed outdoor unit, and you can check and clear both yourself in well under an hour. If you've done that and it still won't go cold, it's a gas leak or a worn-out unit, and that's a tech. We'll come out, look at it, and tell you straight which one you've got — we won't sell you a clean if a clean won't fix it. That's the only way we know how to do this.