Why Is My AC Not Cooling? Common Causes
An AC that runs but does not cool usually has an airflow problem, a refrigerant problem, or an electrical/component fault.
Airflow problems
Blocked filters, a fouled evaporator coil, or a dirty and obstructed outdoor unit all restrict heat transfer. This is the most common cause and often the cheapest to fix.
Refrigerant problems
Low refrigerant means a leak — systems do not consume refrigerant. Recharging without finding the leak simply postpones the failure.
Electrical and component faults
A failed capacitor, faulty fan motor, control board problem or failing compressor will all reduce or stop cooling. These require diagnosis with instruments, not guesswork.
What to check before calling
Confirm the mode and set temperature, clean or check the filters, and make sure the outdoor unit is not blocked by vegetation or stored items. If cooling is still weak, book a technician.