Why Is My Air Conditioner Not Cooling? Is It my AC Filter?

Learn what to look for when your air conditioner isn't cooling and detect the signs reflecting an overworked unit.

Who enjoys sweltering in the summer heat? If you want to ensure that your air conditioner continues to blow cool air in the depth of the summer months, read on for eight reasons your AC is not cooling and how to get it working properly again.

Why is My AC Not Working?

  1. Is There Power? - If the electricity to your home seems fine, but your air conditioner is not turning on, check the breaker. If it's been tripped, your fix may be as easy as flipping that switch.
  2. Improper Settings are on Your Thermostat - You can help your air conditioning unit work efficiently by keeping the thermostat set at a steady temperature. For the best efficiency, you should set the dial to a temperature that feels comfortable, but not too cold. The Department of Energy suggests that having a fan on and setting the temperature at 78 degrees is the perfect energy-saving method. Otherwise, the AC unit would have to kick on and off repeatedly all day to keep the temperatures low.
  3. Dirty or Wrong Size Air Filter - If you're question is "Why is my air conditioner running but not cooling the house?", this may be your answer. As the AC filter clogs with dirt and debris, the efficiency of the system plummets, causing you to pay extra money for less cooling power. In addition, the air conditioner blower must work even harder than normal, which can lead to internal damage. For best results, change your filter every one to three months on average but check it monthly during times with high pollen counts or excessive dust. If you are still unsure how frequently you should be changing your filter, we've got you covered with additional advice.

    How often you replace your filter isn't the only possible reason your air conditioner is not blowing cold air but is running. The wrong air filter size can cause your AC unit to be overworked as well. Always check the make and model of the unit and purchase the correct filter size accordingly. If your old filter does not have labels with the size, grab a tape measure or ruler and take a look at our guidelines on “How to Measure Your Air Filter”.

  4. Faulty Switch - Your air conditioner operates best when the blower can constantly push cooled air through the ducts. Otherwise, the chilled air remains in the system, causing the internal components to freeze and stop working. The most common causes of weak airflow are a clogged air filter or faulty fan switch. If a filter change does not instantly fix the problem, you may need additional diagnostic tests performed by a licensed HVAC professional.
  5. Clogged Drain Lines - Over time, the drain lines in air conditioners get clogged with debris. Once the drain lines are clogged, the air conditioner cannot adequately remove moisture from the air to cool it to optimal temperatures, resulting in your home central air conditioner not blowing cold air. As part of your seasonal cleaning, try to clear out the drain lines to keep your AC unit efficiently producing cool air. If you are unsure of the location of your drain line, set up a HVAC consultation. An expert may be able to show the location of your drain line.
  6. Closed Vent Flaps - The AC unit utilizes exterior vent flaps to release warm air and moisture left over from the cooling process. When the vent flaps are turned to the closed position, the warm air remains in the case and kicks the system into overdrive. When this happens, you may notice that the air coming out of your interior vents feels warmer than usual.
  7. Wrong Unit Size - When you purchase a new air conditioner, it is necessary to match its size to the square footage of your home to avoid overworking the system. An improperly sized air conditioner will work too hard and too long as it attempts to cool the space. This will cause it to develop premature wear and damage that often leads to the failure of internal parts.
  8. Un-insulated Ducts - If your air conditioner ducts are not properly insulated, the cooled air may rise in temperature before it enters the room. Since wildlife like squirrels and raccoons can remove this material from the ducts, be sure to double check the insulation on a regular basis to avoid accidentally overworking the cooling system.

Ways to reduce stress on your air conditioning unit

By paying close attention to the areas listed above, you can make sure your air conditioning unit produces adequate amounts of cool air without causing excessive damage to the internal parts. When you are preparing the air conditioner for summer, for example, you can double check each potential problem area to ensure your system is ready to go before powering it up full-time. You will be rewarded with an AC system that maintains comfortable temperatures in your home without fail.

Preventative care methods like a yearly check-up of your AC unit are more likely to detect any recurring problems. AC units are very expensive and should last an average of 20 years. Proper care throughout your ownership will keep your unit in the best shape possible so you don't have to worry about your air conditioner not cooling or your unit completely giving out during the time you need it most.

Looking for more summer tips? Learn what temperature you should be setting your AC unit to achieve balance between energy efficiency and comfortable living.

The experts at Home Air Guides offer the best air conditioner resources for buying and learning about air conditioning units.

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