When the fan runs but the air stays warm, the refrigeration side has stopped working rather than the whole system. The usual causes are a frozen evaporator coil from a dirty filter or low refrigerant, a failed capacitor stopping the compressor, a tripped outdoor disconnect, or a condenser coil packed with grass clippings and cottonwood. An outdoor fan that will not spin while the unit hums is most often a capacitor, and running the system in that state risks the compressor.
If ice has formed, switching to off with the fan on for a few hours will thaw it, but thawing is not the repair. Unless the airflow or refrigerant cause is fixed, the coil refreezes within days. Pro HVAC connects homeowners in Worthington, OH with HVAC professionals. Call (321) 463-9811.