Why is my AC running but not cooling my house?

If you can see or hear your air conditioner running outside and feel air coming through the vents in your home, but it is not cool or cold air, you have a problem. But what is it? We will go over some common causes in this article. Keep reading to find out more about why your air conditioning is not working.

Dirty Filter

One of the most likely problems with your AC not cooling, is that the filter has become excessively dirty. Once the filter has become dirty enough that a proper amount of airflow cannot pass through your indoor unit, your indoor coil will begin to freeze, which will continue to worsen the airflow problem.  

Once the indoor coil has become sufficiently frozen, your outdoor unit will build up ice, which is the most common thing when people notice the problem. The solution, of course, is to change your dirty filter with a nice clean one, turn your unit off until it thaws out, and then let it run again.

Low Refrigerant

Most homeowners seem to think that this is what’s wrong with their unit, but it is not always the case. If your unit suffers from low refrigerant, it can act similarly to a dirty filter.  

When your unit becomes low on refrigerant, its operating temperature drops below thirty-two degrees. Once this happens, the coils will begin to freeze, just like with a dirty filter. This must be diagnosed and remedied by a professional service technician.


If you look at your outdoor unit and see that the fan on top is running as usual, but there is still the same pressure of warm air blowing out of your inside vents, it may be the capacitor.  

Your capacitor is an electric component inside your condenser that keeps your air conditioner running. It has two sides, one for the fan and one for the compressor that pumps the refrigerant.  

If the side that helps the compressor run has failed, you are not pumping refrigerant or cooling the air coming into your home. If the fan is still running, it may lead you to believe that the unit is operating correctly.  

Capacitors can be extremely dangerous if mishandled and should only be diagnosed and replaced by a professional service technician.

Dirty Coils

This can happen in your outdoor unit and prevent your air conditioner from cooling. Things like mowing grass toward your air conditioner, pollen, dust, dog hair, and other things can get pulled into your outdoor coil and begin to clog it up. You should take a garden hose and spray your coil regularly. Make sure to spray downward to ensure you are pushing any dirt and grime to the bottom and not further into the coil.

You could also have a dirty indoor coil. A dirty indoor coil could be caused by not using a quality air filter or not using one at all. Indoor coils commonly get dirty, and when they do, it will restrict the airflow in the same way that a dirty filter does. Once the airflow is limited, it will begin to freeze.  

It is always a good idea for a homeowner to spray their outdoor unit with a garden hose, but it is not recommended that a homeowner clean their indoor coil. A professional service technician will be able to use chemicals, brushes, and sprayers to clean your coils thoroughly.