An air conditioner that runs but doesn’t cool tends to fail on the hottest, most humid Chicago day of the year. Here are the causes technicians find most, and what you can check.
1. Thermostat settings
Set to Cool, fan on Auto, a few degrees below room temperature. With the fan on On, you’ll feel uncooled air between cycles.
2. Dirty filter
A clogged filter cuts airflow, the indoor coil gets too cold and can freeze. Replace it.
3. Dirty outdoor coil
The condenser coil sheds heat outdoors. Cottonwood fluff, grass and dirt can blanket it in a Chicago June. Gently hose it from the inside out with the power off.
4. Failed capacitor
The most common summer repair. If the outdoor unit hums but the fan doesn’t spin, or the fan runs but the compressor doesn’t, a capacitor is a likely suspect.
5. Low refrigerant
Refrigerant isn’t used up; low refrigerant means a leak. Signs include ice on the copper line, weak cooling and long run times. The leak should be found and fixed, not just topped up.
6. Frozen evaporator coil
Ice on the indoor coil blocks airflow. Turn the AC off, run the fan to thaw it, then find out why it froze: airflow or refrigerant.
7. Leaky ducts
Cool air lost into an attic or basement never reaches the rooms. Upstairs bedrooms suffer most.
8. An undersized or aging system
A system that keeps up in June but not in a 95-degree heat wave may be undersized or simply worn out. Around 15 years is a typical lifespan.
Before you call
- Check both breakers and the outdoor disconnect.
- Replace the filter.
- Clear debris around the outdoor unit.
- Look for ice; if present, turn the AC off and run the fan.
Still warm? Call (312) 924-7223 for AC repair in Chicago.