It’s 35 degrees. Your air conditioner is running — you can hear it, the unit is on, the fan is blowing — but the room isn’t cooling down. If you’ve ever experienced this, you’ll know the particular frustration of a system that appears to be doing its job while very clearly not doing its job.

The good news is that in most cases, there’s an identifiable cause. The better news is that some of those causes are things you can check yourself in five minutes. The important news is that others aren’t — and attempting to fix them without the right certification is not just ineffective, it’s illegal. Here’s how to tell the difference.

Start With the Obvious

Before calling a technician, there are a few quick checks worth doing. First, the filter. A severely blocked filter will restrict airflow to the point where your system is technically running but moving almost no conditioned air into the room. If your filter hasn’t been cleaned in several months — and especially during Hervey Bay’s dusty, humid summers — this is the first thing to check. Most split system filters slide out from behind the indoor unit’s front panel and can be vacuumed or rinsed clean.

Second, check your thermostat setting. It sounds almost too simple, but settings can be accidentally changed, particularly on remote-controlled units. Confirm the mode is set to cooling (not fan-only), that the set temperature is lower than the current room temperature, and that the timer hasn’t accidentally been activated.

Third, look at the outdoor unit. Is there anything obstructing it — overgrown plants, a garden chair, debris from a recent storm? The outdoor unit needs clear airflow around it to reject heat effectively. If it’s been blocked or covered, that alone can significantly reduce your system’s cooling capacity.

Low Refrigerant: The Most Common Culprit

If the filter is clean, settings are correct, and the outdoor unit has clear airflow, the most likely explanation is low refrigerant — commonly called a “regas” situation in Australia. Refrigerant is the substance that carries heat out of your home. When the system is low on it, cooling performance drops noticeably, and in severe cases the indoor coil can freeze over entirely, which creates ice on the unit and water dripping onto the floor.

Refrigerant doesn’t simply run out like petrol. If levels are low, it means there’s a leak somewhere in the system — a loose fitting, a small crack in a coil, or a failing component. Simply topping it up without finding and fixing the leak is a short-term solution that will see the problem return.

Importantly, handling refrigerant in Australia requires an ARCtick certification. It’s a legal requirement, not a guideline. Any unlicensed person who attempts to regas a system is operating illegally. All JM Air & Refrigeration technicians are fully ARCtick certified, which means they can diagnose the leak, repair it, and restore refrigerant levels to manufacturer specifications.

A Frozen Coil — and What Causes It

If you notice ice forming on the indoor unit or the pipes running to it, your evaporator coil has frozen over. This happens for two main reasons: severely restricted airflow (usually from a blocked filter) or low refrigerant. In both cases, the coil gets too cold and moisture in the air freezes on contact with it.

The fix starts with turning the system off and letting it defrost — attempting to run it while frozen will cause no cooling at all, as the ice acts as an insulator. Once defrosted, if the filter was the cause, a thorough clean should resolve it. If the issue returns, refrigerant is likely the culprit and a technician is needed.

Compressor or Electrical Faults

If everything checks out externally and the system still isn’t cooling, you may be dealing with a compressor issue or an electrical fault. The compressor is the heart of the air conditioning system — it pressurises the refrigerant and drives the entire cooling cycle. When it starts failing, cooling performance drops off and eventually the system stops cooling altogether.

Compressor faults are typically accompanied by unusual noises — a grinding, clanking, or hard starting sound when the system kicks on — or by the outdoor unit shutting off shortly after starting. Electrical faults, including failing capacitors or contactor issues, can produce similar symptoms.

These are not DIY repairs. Diagnosis and rectification require both electrical licensing and refrigeration certification. Attempting to access internal components of a refrigerant-bearing system without the appropriate licence isn’t just dangerous — it creates serious liability issues.

Is Your System Simply the Wrong Size?

One final and often overlooked cause: your air conditioner may simply be undersized for the space you’re asking it to cool. A 2.5kW unit installed in a large open-plan living area with high ceilings, west-facing windows, and poor insulation is never going to perform adequately on a 38-degree Hervey Bay afternoon — no matter how well-serviced it is.

If your system is several years old and was installed before a renovation that expanded the space, or if you’ve always felt like it was barely keeping up, a sizing assessment is worthwhile. A properly sized replacement will feel like a transformation. For more information on our air conditioning installation services.

When to Call JM Air & Refrigeration

If you’ve checked the filter, thermostat, and outdoor unit and the system still isn’t cooling, it’s time to call a professional. In Hervey Bay’s summer heat, a non-functioning air conditioner isn’t just uncomfortable — for elderly residents or young children, it can become a health concern quickly.

The JM Air & Refrigeration team is local, licensed, and carries the tools and parts to diagnose most common faults on the first visit. We’ll give you a clear explanation of what’s wrong and what it will take to fix it — no jargon, no inflated estimates.

Air con running but not cooling? Call JM Air and Refrigeration in Hervey Bay on 07 3132 3665 for fast, honest diagnosis and repair. We’ll find the problem and fix it properly.