Why your AC is running but not cooling - dirty filters, frozen coils, bad capacitors, low refrigerant and more, plus what to check before calling for AC repair.
A filter packed with dust starves the evaporator coil of airflow. The coil gets too cold, ice forms, and cooling collapses. Replace the filter first — it is the single most common cause of AC-not-cooling calls.
Ice on the indoor coil or copper lines means airflow or refrigerant is wrong. Switch the system to fan-only for 2–3 hours to thaw it, then have the cause diagnosed. Running a frozen system risks compressor damage.
A weak capacitor keeps the compressor or condenser fan from starting. You may hear a hum or clicking outside with no fan spin. This is an inexpensive, same-visit repair.
Air conditioners do not consume refrigerant. If it is low, there is a leak — topping it off without repairing the leak wastes money and eventually kills the compressor.
The outdoor coil rejects heat. Cover it in grass clippings, cottonwood or dust and head pressure spikes while cooling capacity drops 20–30%.
If the outdoor fan is not turning while the compressor runs, shut the system off immediately to prevent overheating damage.
Weak airflow at the registers with a cold coil usually points to the indoor blower — a failing motor, bad ECM module, or a wheel caked with dirt.
Dead batteries, a missing C-wire, or a thermostat in the wrong mode can mimic total system failure. Verify Cool mode and a setpoint well below room temperature.
If everything else checks out and the temperature split across the coil is under 15°F, the compressor may be losing capacity — a repair-versus-replace conversation.
Guesswork costs more than a service call. Talk to a licensed technician now.
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