Why is my air conditioning system not cooling my house?

March 10, 2023

air conditioning system not cooling

A good answer sometimes requires more questions and more information to understand the problem. Case in point – did the air conditioning system previously cool the house acceptably? If so, what has changed so that it no longer cools the house? Air conditioning systems are designed and sized specifically for the home in which they are installed, based on the size of the home, the location, and the heat load the house will be subjected to when the unit is operating. This term refers to how much heat exists outside the home (how hot is it outside?), inside the home (how many people live in the home, how many showers do they take, how much cooking goes on), how many windows there are and how well the home is insulated. Assuming the existing system at some point cooled the house adequately, then we need to consider what may have changed.

Why is my Home AC Not Cooling?


For purposes of this discussion, we will assume that none of the following have occurred:

  • The climate has not significantly changed due to a global emergency;
  • Your son’s high school basketball team has not moved in with you;
  • You did not add on to the house and think the existing system could handle two extra bedrooms and a bath.

Heat Load

Then, let’s consider some things that really could affect the heat load on the house:

  • Have there been any large shade trees removed from the yard (more sunshine beating down on the roof);
  • Was there a new patio, deck or pool added near the house (all that reflected light can really heat up the outside walls).
  • Were there recently any workmen in the area of the equipment that could have accidentally damaged the air conditioning system and affected the performance.

Poor System Performance

Let’s also consider some other possible sources of poor system performance:

  • A refrigerant leak in the system;
  • Lack of routine maintenance of the system – a dirty coil is less efficient and cannot cool and/or dehumidify the air passing through it as well.
  • A clogged return air filter or dirty ducts do not move as much air through the system.
  • Some forms of blown attic insulation can settle over time and provide significantly less protection against the hot air in the attic.
  • Over the years have a lot of things been stored in the attic, possibly compressing the insulation, and reducing its effectiveness?
  • Has something altered the attic ventilation, thereby increasing the temperature in the attic (frozen roof turbines, bird nests in the gable vents)?
  • Has the overflow pan beneath the unit filled enabling the “kill” switch to engage thereby turning the unit off?

All the above are things to look for as possible reasons why an air conditioning system no longer cools a house adequately. A handy homeowner can check many of these and a competent air conditioning contractor can quickly help with the rest.

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