AC Running but Not Cooling? 5 Checks Before You Call for Service

Air is moving. The system sounds like it's working. But the air coming out isn't cold, and the house keeps creeping warmer. Before you book a service call in the middle of a heat wave — when everyone's booked out days — run these five checks.

Standing rule, every page: if you ever smell gas — rotten eggs — leave the house and call your gas company from outside. That outranks everything below.

1. Thermostat: COOL, AUTO, and below room temperature

Mode set to COOL — not FAN, which moves air without cooling it. Fan set to AUTO. Target temperature at least 3 degrees below the current room reading. If the screen is blank, try fresh batteries. This paragraph closes more "broken AC" calls than any part on a truck.

2. Is the outdoor unit actually running?

Central air is a two-part system: the indoor blower moves air, the outdoor unit makes it cold. If the inside fan runs but the outdoor unit sits silent, you'll get exactly this symptom — moving air, no cooling.

Stand next to the outdoor unit while the system is calling for cool. Hear nothing? Check your breaker panel for a breaker labeled AC, condenser, or outdoor unit. If it's tripped, reset it once — fully off, then on. If it trips again, stop and call; repeated resets can cause real damage.

3. The filter

A clogged filter can choke airflow enough that the system barely cools — and in the worst case, the indoor coil ices over and blocks air entirely. Hold the filter to a light; can't see through it, replace it.

If you see ice anywhere on the copper lines or the indoor unit, switch the system to OFF and the fan to ON, and let it thaw for a few hours before trying again. (Ice has its own page: Ice on the AC line.)

4. The outdoor unit's breathing room

The outdoor unit sheds heat through its side coils. If it's wrapped in cottonwood fluff, grass clippings, or hedge, it can't dump heat and your cooling fades. Look at it. If the fins are matted with debris, gently rinse them with a garden hose (system off) and clear plants back a couple of feet.

5. Doors, windows, and the afternoon sun

Not every warm house is a broken AC. A house full of west-facing glass at 5 PM in July can outrun a healthy system by a few degrees. If the AC keeps up in the morning and loses ground in late afternoon, close blinds on the sunny side before assuming a failure.

Still warm? Get ahead of the service call

If these all check out, the likely suspects — low refrigerant, a failing capacitor, a compressor issue — need a technician and a gauge set.

Ten minutes with our free troubleshooter first means you call with the simple stuff already ruled out, and a summary the dispatcher can hand the tech.

Related symptoms

• Ice on the AC line
• AC won't turn on
• AC leaking water

Start the free troubleshooter → Free. No sign-up. Know before you call.

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