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Why is My AC Running Constantly
19 Sep

Why is My AC Running Constantly

There are numerous reasons why your A/C system may seem to be running non-stop.

The truth is, this may not always be a bad thing. Some of the reasons may indicate a problem with your system and others may alert you to other issues in your home that you can take steps to correct.

7 Common Causes Your A/C Runs Non-Stop

1. Improper Size and Installation Can be Damaging It's important to start our discussion with this fact: "a properly sized, energy-efficient central air conditioning system will run fairly continuously in the summer to maintain a constant, desired temperature in your home. These systems operate at their highest efficiency level when allowed to do their job at "full tilt."

Unit Too Small: If your central air conditioner is too small, then it is going to have to work harder to cool your home. Over time, this will increase the wear and tear on your unit and reduce its life. You will also never achieve the desired coolness in your home, even though the system runs often. In addition, breakdowns will be likely.

Unit Too Large: If your system is too large, it won't effectively remove moisture from the air in your home, resulting in an output of moist, clammy air. It will actually have shorter run times than it should and use excessive amounts of electricity, resulting in higher utility bills.

Wrong Duct Size: The size of your ductwork should be relative to the size of your air conditioning unit. If your ducts are the wrong size, they may not be able to handle the airflow or distribute cool air efficiently to all parts of the home. 75% of air conditioning problems can be resolved by the correct method of installation in combination with the right-sized air conditioning unit. If not the size, let's take a look at what you may be able to fix immediately. It's as easy as checking your filter.

2. Check Your Air Filter for Immediate Relief When was the last time you changed your air filter? If it's been a while, it's probably dirty restricting airflow. This will cut down on the amount of cool air your air conditioner can produce, which in turn will make your A/C seem to run more throughout the day. When your air filter is clogged, your air handler must work harder to compensate. Would you believe the most common reason an HVAC breaks down is due to a dirty filter? A dirty filter makes your system work harder causing it to overheat. Cleaning the debris that builds up on your filters will aid with the flow of air. Clean or replace your filters once a month or as recommended by the manufacturer. Without enough air flowing over the coils, the system can’t remove humidity and cool the air to the set temperature, so it keeps running when it shouldn’t. This brings us to another possibility...

3. Air Conditioner Coils Covered in Dirt? Dirt, in the form of grass clippings, pet hair or mud will block the airflow. What happens with reduced airflow?... diminished performance. (lower energy efficiency and perhaps A/C runs non-stop) Homeowners should have a service technician perform a system check-up annually. They will inspect your condenser and evaporator coils. Condenser coils need to be cleaned because they are exposed to outdoor elements. You can maintain condenser coil efficiency by simply hosing down the unit. Turn off any electrical power first to your system. The evaporator coils are harder to get at. The visual check is not as simple as the condenser coils. But they are in need of maintenance as well. Griffith Energy Services sums it up nicely... "Because the evaporator coil is continuously exposed to airflow circulated by the blower, it’s susceptible to buildup of dust or dirt. When airborne particles form a layer on coil surfaces, the efficiency of the all-important heat transfer from the air to the refrigerant is diminished. This can result in poor cooling performance and higher operating costs as the system runs longer “on” cycles to meet thermostat settings." Annual maintenance is the key to removing this unwanted dirt and dust.

4. Thermostat Not Working - Here's What to Do If your system seems never shut off, there may be an issue with your thermostat. It may be that your home has reached the correct temperature, but the thermostat is not registering the conditions in the home. In this case, your A/C unit will continue running. One way to check the thermostat is to place another thermometer near the location of the thermostat. After an hour or two, check the reading. If it is at or near your desired home temperature, there may be a problem with your thermostat. Thermostats are typically reliable but they can run into problems. HomeGuides explains step by step How to Tell if Your Thermostat is Bad.

Here's a quick 2 step process to get the ball rolling...

Step 1: Set the thermostat at least 5 degrees higher or lower than your normal setting, depending on the season. Set it 5 degrees lower during the cooling season. Check that the device comes on.

Step 2: Check that the thermostat is correctly set to "Heat" or "Cool". Check that the main circuit breaker for the air conditioner is in the "On" position. If you find these steps did not quickly fix the issue, continue to troubleshoot by turning the power "off" for the air conditioning system at its appropriate circuit breaker. You can continue with the steps offered by home guides.

5. Air Leaks or Poor Insulation - Time to Seal Poor sealing or insufficient insulation is another common culprit which can cause your unit to run constantly and inefficiently. If your home is not closed up tight while your A/C system is in use, you may be losing that precious cool air that you need during the summer through small holes or non-insulated walls or roofs. If you are losing the cool air in this way, your home may never reach your desired temperature, causing the A/C unit to run more than needed. Our related article: 8 No Cost Ways to Improve Air Conditioning Efficiency gives you some background on why sealing and insulating your home is so important, especially for A/C efficiency. One Hour Air Conditioning & Heating explains How Basement Air Leaks Will Hurt You Come Summer. The theory is based on the "law that cold air is denser and heavier than warm air. During summer, the pressure created by the hot outdoor air pushes air-conditioned air lower." If there are air leaks in your basement, the air is forced out. This can negatively impact your summer cooling bills.

6. Air Conditioning Unit Needs Maintenance As stated, air conditioning units need regular maintenance to continue running smoothly, much like other appliances in your home. Ideally, maintenance should happen twice a year, in the spring before the warm weather hits and in the early fall after things have cooled off and it is no longer in use. If your system is not clean, including your ducts, coils, and air filter, you will likely encounter airflow problems and inefficient cycling. A professional technician will check to make sure everything is clean and lubricated. He/she will replace worn parts and confirm that the thermostat is working properly. Regular maintenance of your A/C unit will not only help ensure that your unit is in good working order, but it will also extend the life of your cooling system.

7. Your Unit is Old And Needs to be Replaced Air conditioners have a life span. Even if your unit has been properly maintained, it will eventually wear out. At this point, you may want to consider replacing your old, inefficient unit with a new one. This will save you money in the long run, because newer units run much more efficiently than old ones. Blue Dot Services created a handy infographic on How to Keep Your Cool: Top Signs Your HVAC System Needs Attention. Newer, high-efficiency air conditioning systems use about half the electricity of an old unit. Be sure to check the SEER ratings if you decide to purchase a new system. The higher the SEER rating (Seasonal Energy Efficiency Ratio), the more efficient the system.


Address issues before they become problems. Any of the above reasons can cause your air conditioner to run more often than it needs to, which will cost you more money. Your best bet is to contact a professional and let them know you have an A/C system running constantly if you are concerned. Chances are it is something simple. Even if it is a more significant problem, dealing with the repairs now will greatly reduce your bills in the future.