Start with the easy stuff
A surprising number of "broken" air conditioners are really a setting, a switch or a filter. These checks are safe and take about five minutes.
The checklist
- Thermostat: make sure it's set to COOL, the set temperature is below the room temperature, and the fan is on AUTO.
- Thermostat batteries: a blank or dim screen often just means new batteries.
- Breaker panel: look for a tripped breaker labeled AC, condenser or furnace. Reset it once. If it trips again, stop and call.
- Outdoor shut-off: the small box on the wall near the outdoor unit should be switched on or have its pull-out block in place.
- Air filter: a clogged filter can choke airflow and even freeze the coil. Replace it if it looks gray.
- Vents and returns: open the supply vents and make sure furniture isn't blocking the big return grille.
- Outdoor unit: clear leaves, weeds and anything stacked against it. It needs a couple of feet of open space to breathe.
- Ice on the lines: if you see frost or ice, turn the system OFF and the fan ON for a few hours to thaw it, then call. Ice means an airflow or refrigerant problem.
When to stop and call
- The breaker trips again after one reset
- You smell burning, or hear loud buzzing or banging
- The outdoor fan isn't spinning while the unit hums
- Water is leaking from the indoor unit
- The house is getting dangerously hot and someone at home has health concerns
Hot day? Keep cool while you wait
Close blinds on sunny windows, run ceiling fans, and avoid using the oven. If indoor temperatures climb into the 90s, anyone with health concerns should go somewhere cool. San Diego County opens Cool Zones at libraries and community centers during heat waves.