An air conditioner that is running but not cooling your home properly can have several possible causes. Some are simple things you can check yourself, while others require an HVAC professional.
Before assuming the AC unit has failed, work through a few basic checks.
1. Check the Thermostat
Make sure the thermostat is set to Cool and that the temperature setting is lower than the current room temperature.
Also check whether the fan is set to Auto rather than On. When set to On, the fan may continue blowing even when the system is not actively cooling.
2. Check the Air Filter
A dirty air filter can restrict airflow through the system.
If the filter is heavily covered with dust and debris, replace or clean it according to the manufacturer’s instructions.
Regular filter maintenance can improve airflow and help your air conditioner operate more efficiently.
3. Check the Air Vents
Make sure supply vents around the home are open and are not blocked by furniture, curtains, boxes, or other objects.
Restricted airflow can make rooms feel warmer even when the AC system is operating.
4. Check the Outdoor Unit
If your system has an outdoor unit, look at it from a safe distance while the AC is operating.
Leaves, vegetation, dirt, and other debris around the unit can interfere with airflow.
Keep the surrounding area reasonably clear, but do not open the unit or touch electrical components.
5. Look for Ice
Ice forming on refrigerant lines or parts of the indoor or outdoor system is not normal.
Restricted airflow and other system problems can contribute to freezing.
If you notice significant ice buildup, turn the cooling system off and arrange for the cause to be investigated rather than repeatedly running it.
6. Consider How Long the AC Has Been Running
On extremely hot days, an air conditioner may need considerable time to lower the indoor temperature.
However, if the system runs continuously without producing noticeably cooler air, there may be a problem requiring professional diagnosis.
When Should You Call an HVAC Professional?
Consider calling a qualified HVAC technician if:
- The AC runs but produces little or no cool air
- Ice repeatedly forms on the system
- The outdoor unit is not operating
- The system repeatedly shuts itself off
- You hear unusual noises
- You notice burning smells
- The problem continues after checking the thermostat, filter, and vents
Avoid opening electrical panels or attempting refrigerant repairs yourself. Those parts of an air-conditioning system should be handled by a qualified professional.