Start with the simple checks
- Thermostat set to Cool, fan on Auto, and set a few degrees below room temperature.
- Replace the air filter if it is dirty.
- Check both breakers, indoor and outdoor.
- Go outside: is the fan on top of the outdoor unit spinning?
The usual causes
Outdoor unit not running
If the indoor fan runs but the outdoor unit is silent or humming, a failed capacitor or contactor is the most common cause. These are electrical parts a technician should replace, because the capacitor can hold a dangerous charge.
Ice on the lines or coil
Ice means the indoor coil is too cold, usually from low airflow or low refrigerant. Turn the system off and let it thaw before running it again. See why an AC freezes up.
Dirty outdoor coil
Cottonwood, pollen, and grass clippings can blanket the outdoor coil so the system cannot release heat. This is one reason a spring tune up matters in the Triangle.
Low refrigerant
Refrigerant is not used up. If it is low, there is a leak. Adding refrigerant without finding the leak is a temporary fix.
When to call
If the simple checks do not solve it, turn the system off to protect the compressor and schedule AC repair.
