Aircond not cold: common causes and checks
Why an aircond stops cooling, the causes from a dirty filter to low refrigerant, safe checks, and when to call a technician.
What usually causes it
A dirty filter is the most common cause of an aircond that is not cold.
Low refrigerant is another cause of an aircond that is not cold. A low charge means there is a leak somewhere in the system, and a leak needs professional detection and repair.
A frozen coil is a further cause to recognise: switch the unit off immediately and let it thaw. Compressor problems need an assessment by a certified technician.
Checks you can do safely
Switch the unit off at the isolator before touching anything beyond the filter.
Clean the filter. Service providers commonly advise cleaning filters every 2-4 weeks in dusty conditions. Check the thermostat is on Cool and set below the room temperature.
Providers advise cleaning the outdoor unit’s condenser every 3-6 months. If the coil has frozen, switch the unit off immediately and let it thaw.
When to call a technician
Leave refrigerant, compressor, and electrical work to a qualified technician.
Call one for low refrigerant, which needs leak detection and repair, and for compressor problems, which need an assessment by a certified technician.
Updated 4 Oct 2026