Why is my air conditioner not cooling or heating properly?

An air conditioner that is not cooling or heating properly usually has an airflow problem, a wrong setting, a unit that is too small for the room, or a refrigerant fault. Some causes are simple, but refrigerant and electrical faults need a licensed technician, so note the symptoms and call rather than investigating the unit yourself.

What makes an air conditioner stop cooling or heating well?

Most split systems, ducted systems and reverse-cycle units (one machine that both cools and heats) work by moving heat from one place to another. Anything that interrupts that process shows up as weak performance. The common causes are:

• Restricted airflow. Dust build-up on filters or coils, or blocked vents, reduces how much air the system can move.
• A low refrigerant charge. Refrigerant is the fluid that carries heat. It is sealed inside the system, so a shortage normally means there is a leak somewhere.
• The wrong mode or temperature. A unit in fan or dry mode, or with a set temperature close to the room temperature, will not cool or heat much.
• A unit that is too small. A system that is undersized for the room, or a room with a lot of sun or poor insulation, can run all day and never catch up.
• A fault in the outdoor unit or controls. A failing fan, compressor or control board can reduce output or stop it altogether.

Why does it feel humid but not cold?

In Brisbane and across south-east Queensland, summer air carries a lot of moisture. An air conditioner has to remove that moisture as well as lower the temperature, so a room can feel clammy for some time after the unit starts. That can be normal on a very humid day, especially in a large or sunny room. If the room never reaches a comfortable level over a long period, the system may be undersized or have a fault.

What should I do first?

Using the remote or app as normal, check that the mode and temperature are suitable for what you want. Close doors and windows in the room while the unit runs. The owner’s manual explains the modes and the manufacturer’s maintenance guidance for your model, so it is worth reading. Do not open the unit, remove covers or try to adjust anything inside or outside.

Can I top up the gas myself?

No. Refrigerant is sealed in, so it does not get used up like fuel. A low charge points to a leak, which needs to be found and repaired. In Australia, working with refrigerant requires a licence from the Australian Refrigeration Council (ARC), and DIY gas kits are not a safe or lawful option. You can find out more at arctick.org.

Why might a newer unit still struggle?

The size of the system matters as much as its age. A unit that is too small for the room, or one placed where the sun hits the room all afternoon, will struggle. A licensed professional can assess room size, ceiling height, sun exposure, insulation and layout to judge whether the system suits the space.

What does a technician do on a visit?

A licensed technician will check how the system is performing, look at airflow and the condition of the indoor and outdoor units, and inspect for refrigerant leaks and electrical faults. They will explain what they find and what repair, if any, is needed. Keeping a note of your symptoms and photos of the model label makes the visit faster and more useful.