Why your aircon is not cooling
A unit that runs but does not cool is one of the most common calls a contractor gets, and it has several possible causes. This guide explains how the symptoms differ, so you can describe yours accurately.
Start with the simple things
Before booking anyone, check the filter and the setting. A filter that is packed with dust chokes the airflow, and a unit with poor airflow cools poorly no matter what else is right. Check too that the unit is set to cool rather than fan only, and that the temperature setting is actually below the room temperature.
Then look outside. If the outdoor unit is not running at all, or is running but the fan is not turning, that is a fault rather than a setting. If there is ice on the indoor coil or on the pipe between the units, the unit is telling you something specific, and it is worth mentioning when you book.
One more check costs nothing: make sure the outdoor unit has airflow. A condenser boxed in by shrubs, or sitting in a courtyard where hot air collects, cannot reject its heat, and the unit will underperform on the hottest afternoons even when everything on it is working. Clear the space around it and see whether the cooling changes before you book anyone.
The faults that need a contractor
A failed fan, a worn capacitor, a control board that has given up and a compressor that will not start all present as a unit that is not cooling. None of them can be diagnosed by sound from a distance, and one of them is expensive to replace, which is exactly why a guess is a bad idea.
Sudden loss of cooling, with the unit otherwise behaving normally, is more often one of these faults than a refrigerant problem. Weak cooling that faded over weeks or months points the other way, at a slow leak.
Refrigerant: why the leak comes first
A sealed system does not use its refrigerant up. It circulates in a closed loop on every unit ever made, so a system that is low has lost refrigerant through a joint, a flare, a valve or a crack in a coil. That is why a proper regas starts with a leak test rather than a gas bottle.
Filling a system that is still leaking buys time and nothing else, because the refrigerant will leave by the same route again. A proper job finds the leak, repairs it, pressure tests the loop, then evacuates and charges the system by weight to the maker's specification. Aircon gas refill sets out what that involves.
What to tell the contractor
Give the make and model, the rough age, and what the unit does now: does the indoor fan run, does the outdoor unit start, does anything drip, does anything trip. Say whether the cooling faded slowly or stopped suddenly, because that single detail points in different directions.
If the remote or the indoor display shows an error code, send it. A code can point straight at the fault and save a visit. If you have a service record, mention when the unit was last cleaned. Aircon repair covers what a call-out involves, and how often to service explains the cleaning rhythm that prevents some of these faults.
Frequently asked questions
My aircon runs but blows warm air. Is it out of gas?
It might be, and it might be a failed fan, a blocked coil or a control fault. The only way to know is to test the unit, so book it as a repair and describe what it does.
Can a blocked filter stop the cooling completely?
A badly blocked filter chokes the airflow and the unit cools very poorly, and it is the first thing worth checking. It will not cause a unit to blow warm air indefinitely.
My unit freezes up. What does that mean?
Ice on the indoor coil or the pipe can be a sign of a slow refrigerant loss or an airflow problem. It should be looked at rather than run until it thaws, and the contractor should test rather than guess.
How soon can an aircon be repaired?
That depends on the contractor and the time of year. In a heatwave everyone is booking at once, so report the fault early and describe it accurately.