Why is my AC blowing warm air?

The most common and cheapest-to-fix cause is a dirty air filter restricting airflow — check and replace it first, especially if it hasn't been swapped in the last 60–90 days.

Next, check the thermostat is actually set to 'cool' and the temperature is below the current room temperature, and that batteries (if it's not hardwired) aren't dead. It sounds obvious, but it's a genuinely common false alarm.

If the filter and thermostat both check out, the next likely causes are a low refrigerant charge (often from a slow leak), a frozen evaporator coil, or a failing capacitor or compressor — none of which are safe or legal for a homeowner to diagnose or refill themselves in most states, since refrigerant handling requires EPA certification.

If you hear unusual noises (grinding, hissing, clicking that won't stop) alongside the warm air, that's worth mentioning specifically when you call for service — it narrows down the likely cause before the technician even arrives.