Why is my AC running but not getting cool?

When an air conditioning system runs continuously but fails to lower indoor temperatures, the issue typically stems from airflow restrictions, refrigerant problems, or mechanical failures. One of the most common and easily correctable causes is a severely clogged or dirty air filter, which chokes airflow across the evaporator coil and causes the coil to freeze into a solid block of ice. Other frequent culprits include low refrigerant levels caused by a hidden leak in the copper tubing lines, dirty outdoor condenser coils covered in dirt and debris that prevent heat dissipation, or a malfunctioning outdoor compressor fan motor. Additionally, a faulty thermostat calibration or leaky ductwork running through unconditioned attic spaces can prevent cooled air from effectively reaching the living areas of your home, requiring systematic diagnostic testing.

When an air conditioning system's blower fan and outdoor compressor are actively running, but the air blowing from your home's supply vents remains completely room-temperature or warm, it indicates a failure in the thermal heat transfer cycle. The most common cause is a severely clogged, dirty air filter that restricts airflow across the indoor evaporator coil, causing it to freeze solid into a block of ice and halt cooling performance. Other major culprits include low refrigerant levels caused by a sealed system leak, dirty exterior condenser coils choked with debris, or a failed electrical capacitor preventing the compressor from pumping effectively. Always turn off the thermostat to prevent motor damage. You can verify success by measuring a 15 to 20 degree temperature drop at the vents after cleaning filters.