Air conditioning systems are reliable when maintained, but a handful of faults come up again and again. Knowing the usual causes speeds up diagnosis and repair.
Weak or no cooling
Often caused by low refrigerant (a leak), dirty filters or coils restricting airflow, or a blocked condenser. Check airflow and filters first, then take pressure and superheat/subcooling readings to assess the refrigerant charge.
Icing up
Ice on the indoor coil or suction line usually points to low refrigerant or poor airflow (dirty filter, failed fan). Defrost, then find the root cause rather than just clearing the ice.
Water leaks
Usually a blocked or misaligned condensate drain, allowing water to overflow the tray. Clear the drain and check the slope.
Strange noises
Rattles may be loose panels; grinding or screeching can indicate fan or compressor bearing problems; hissing or bubbling can suggest a refrigerant leak.
System not running
Check the power, thermostat settings, capacitor and any safety cut-outs (such as a high-pressure trip or condensate float switch).
FAQ
Why is my AC blowing warm air? Common causes are low refrigerant from a leak, a dirty filter/coil restricting airflow, or a compressor not running — diagnose airflow first, then the refrigerant circuit.
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