What to Do When Your AC Stops Working in a Heat Wave

It always seems to happen on the hottest day of the year — the AC just stops. Before you panic or start calling around, there are a few things worth checking yourself. Sometimes it's a genuine emergency; sometimes it's a five-minute fix.

1. Check the Thermostat First

Make sure it's set to "cool," not "fan" or "off," and that the temperature is actually set below the current room temperature. If it's a smart thermostat, check that it still has power and hasn't lost its Wi-Fi connection in a way that's stopped it from communicating with the system.

2. Check Your Breaker Panel

AC systems typically have two power connections — one at the indoor air handler or furnace, one at the outdoor condenser. A tripped breaker on either side will shut the whole system down. Check your panel for a breaker that's flipped to the middle or "off" position and reset it once. If it trips again immediately, stop — that's a sign of an electrical fault, not something to keep resetting.

3. Check the Outdoor Unit

Walk outside and look at the condenser. Is the fan spinning? Is it covered in leaves, grass clippings, or debris? A unit that's visually running but not cooling could have a refrigerant issue. A unit that's silent and not running at all could be an electrical or capacitor problem — both are jobs for a technician.

4. Check Your Air Filter

A severely clogged filter can restrict airflow enough to cause the system to ice up internally, which then blocks cooling entirely. If you can see daylight through your filter, it's fine. If it's caked in dust, replace it and give the system 30–60 minutes to see if performance improves once ice (if any) has had a chance to melt.

5. Listen for Warning Signs

Buzzing, clicking that won't stop, grinding, or a burning smell are all reasons to shut the system off at the thermostat and breaker and call for service right away rather than waiting it out. Continuing to run a system that's making these noises can turn a moderate repair into a full replacement.

While You Wait for Help

• Close blinds and curtains on sun-facing windows to cut down on heat gain
• Use fans to keep air moving, especially at night
• Stay hydrated, and check on elderly neighbors or family members without reliable AC
• Avoid using the oven or running heat-generating appliances during the hottest part of the day