Split system not cooling in Melbourne.

Summer heat in Melbourne can reach levels that put your split system at risk.

Not every split system can keep up and you’ll know about it quickly when your room doesn’t actually cool.

From our experience it’s often something small but other times it’s a more complex issue that needs professional attention.

In this guide, we break down the real Melbourne causes behind split systems that won’t cool, so you’ll know about what to do and when to call the experts.

Key Takeaways

  • When a split system runs but won’t cool, there’s always a cause, and Melbourne summers expose it quickly.
  • Heatwaves don’t break systems, they reveal weak ones, especially units that are undersized or worn.
  • Running a struggling air con just compounds the damage, turning small issues into costly repairs fast.

Why isn’t my split system cooling?

  • Dirty filters prevent optimal airflow, putting stress on the system and causing less cooling.
  • A blocked outdoor unit will trap heat, especially during the Melbourne summer heat waves. This could be by not having enough space or debris smothering the system.
  • Low refrigerant means the system can’t absorb heat properly, often caused by a leak. Leak detection is always required before an air conditioner regas.
  • Undersized system will struggle to cool during the hot days even if it’s running continuously.
  • Electrical or sensor faults cause the system to misread temperatures or cycle incorrectly.

Man struggles in heat because split system isn't cooling.

First Things to Check Before Calling a Technician

No need to panic right away, there are some simple checks that you can do before assuming your whole system is broken.

And these catch a lot of people.

Is your split system set correctly?

It’s always the basic stuff that gets people, but is a massive reason.

  • Cool mode
    Your system must be set to cool mode. Any other mode such as heat mode will prevent cooling from distributing throughout your home, causing problems during Melbourne’s summer.
  • Temperature gap
    You need to make sure the temperature you have set is lower than the room. If it’s too close, it probably won’t cool effectively. Set the temperature 3-5 degrees lower than the room.
  • Fan vs auto
    Fan mode will just move air around and will not cool. Be sure to have fan mode off.

Air Conditioner Icons.

Is airflow weak or uneven?

If the airflow is still out of whack or uneven well this can indicate a different issue.

What weak airflow actually means:

Air feels faint, warm, or uneven from the unit. Some rooms cool while others don’t.

What it usually points to:

Dirty filters, blocked coils, or a system starting to struggle under load. These issues reduce cooling fast, especially during peak summer heat.

 

If everything above checks out and cooling still isn’t there, that’s usually the point where a technician needs to step in.

 

The Most Common Reasons Split Systems Don’t Cool in Melbourne

These are undoubtedly the most common reasons why your split system is struggling to cool.

Pay close attention.

 

Dirty or clogged split system filters

Melbourne’s busy lifestyle means you may not have time to clean your split system filters.

This will cause masses of dust, pollen, and debris to get caught in the coils, and filters.

Don’t panic because this is a simple fix by cleaning your filters.

In our 7 essential maintenance tips for split systems in Melbourne we cover how to do this.

Aim to clean your filters once a month to ensure nothing is clogging the system.

dirty and clogged split system filters in Melbourne.

Outdoor unit blocked or overheating

Melbourne has a big issue with outdoor units being blocked or crowded.

With the rise in apartment living we’re seeing split systems installed poorly with inadequate space.

Ultimately this suffocates the outdoor unit.

It’s either covered by plants, leaves or other objects.

Ensure there is enough room around the unit, if not call a technician.

 

Low refrigerant or gas leak

This might be a shock to you but a technician can’t regas an air conditioner without finding and fixing the leak.

It’s dangerous and pointless because it will just lose refrigerant quickly, putting you back to the starting point.

An air conditioner that has no refrigerant is not being stolen by a secret refrigerant thief; it’s leaking.

 

Your split system is too small for the space

This is one of the most common reasons a split system “works”… until it doesn’t.

In apartments or small rooms, a split system should perform quite well.

But open plan homes with larger living spaces or higher ceilings a split system that isn’t sized correctly can struggle.

That’s why so many units seem fine most of the year, then fall apart on 35°C Melbourne days. The system hasn’t suddenly broken. It’s just not sized right.

If you’re not sure whether your unit matches your space, check out our air conditioning size calculator.

 

Electrical or sensor faults

Common signs of an electrical or thermostat fault are short cycling or inconsistent temperatures.

If your unit is turning on and off, it puts extra strain on your system pointing to a faulty sensor, wiring issue or even a control board problem.

If the split system has inconsistent temperatures, whereby one minute it’s cool then the next it’s hot, the thermostat is probably not reading the room properly.

You can’t handle electrical or thermostat issues yourself, as they are technical and it can be dangerous. 

A licenced technician is the only one that can properly diagnose and fix the issue.

 

Poor or rushed installation

These can be some of the worst experiences when you install a fresh split system and it doesn’t even survive the first summer.

It does happen.

However usually by cowboy installers that rush the job.

You might see incorrect pipe length, bad placement, or just wrong wiring.

Electricians can install split systems, but we never recommend this as they don’t have a full ARC licence and only need a 2 day practical course to complete it.

Always go with fully licenced ARCtick air conditioning technicians who install with care.

 

Older split systems losing efficiency

Just like anything over time systems wear down.

When you hit the 10-15 year mark the parts inside the air conditioner get less efficient.

We often see the motors that aren’t as strong, compressors working harder even with servicing the wear and tear adds up.

The system often needs more power to do what it used to to do because the fans are moving air and coils aren’t transferring heat like they used to.

Replacement is often a better option when they get into this advanced age, because of the increasing power, and repair costs.

You can find out exactly how long an air conditioner lasts in our guide.

 

Why Split Systems Struggle More During Melbourne Heatwaves

Melbourne’s heatwaves shock the system because it can be 22 then the next day is 40 degrees, this is where the air conditioners get tested.

Air conditioners need to release heat outside so when the outdoor temperatures are skyrocketing, it can’t do it as fast, putting strain on the system

Heatwaves will also expose your setup if the air con is too small.

It can be fine all year but up at the height of summer around 35-40 degrees it all goes wrong.

You’ll get that frustrating feeling of the system never cooling enough, with weak airflow, and higher power bills.

The system isn’t broken, it just wasn’t ready for that heat.

 

What You Can Safely Do Yourself (And What You Shouldn’t)

There are a few things you can do as mentioned before.

Check the filters, settings and everything exterior to the inside and outside unit for any abnormalities.

Any technical parts deep inside the units, it’s best to leave it to an air conditioning technician for expert ac repair.

 

How to Stop Your Split System From Losing Cooling Again

The number 1 way to prevent your split system from failing when you need it most is to get a split system service at least once a year preferably before summer.

This is designed to make sure your system is running efficiently and will continue to run during the peak heat.

We also recommend checking your filters at least once a month and making sure there aren’t obvious obstructions.

It might be tempting to blast the cooling in summer but if you maintain a reasonable cooling temperature of around 24 degrees Celsius, you won’t overload the system.

Common Questions About Split Systems Not Cooling

Can low gas damage the compressor?

Yes. When refrigerant is low, the compressor has to work harder to move heat. Over time that extra strain can cause overheating and internal damage, which is one of the most expensive failures in a split system.

Why does it cool at night but not during the day?

At night the outside air is cooler, so the system can dump heat more easily. During the day, especially in Melbourne heat, the outdoor unit struggles to release heat, making cooling feel weak or non-existent.

How long should it take to feel cold air?

You should feel noticeably cooler air within 5 to 10 minutes. If it’s just blowing room temperature air after that, something isn’t right.

Is it safe to keep running it?

Short term is usually okay, but running a struggling system for days can cause bigger issues. If it’s not cooling properly, it’s better to switch it off and have it checked before more damage is done.

Book in a Split System Repair Today

If your split system is experiencing any of these problems, it’s best to book in a split system repair from a certified air conditioning technician.

At Thomas Air Conditioning, we provide long-lasting solutions to split systems issues, whether you need maintenance to get through the summer or something has gone wrong, we can ensure reliable cooling all year-round.

Don’t let the problems fester, if you’re not sure, book a service check or call us on (03) 9553 3993