It doesn't take long for the average air conditioner to bring your home's indoor temperatures down to your desired levels. In most cases, an A/C system that's in good shape can cool off a home within 10 to 15 minutes before turning off. However, there are several issues that could make an A/C system run constantly without shutting off.
#1: Clogged Air Filter
A clogged air filter can block air from entering the A/C unit. This not only adds stress on the blower motor as it attempts to pull air through the clogged filter, but it can also cause your A/C to run continuously in an effort to keep your home cool. To keep this from happening, you should change your air filter once every 3 months, at minimum. If you have pets or allergies, you may need to change the filter on a monthly basis.
#2: Dirty or Frozen Coils
The evaporator and condenser coils are designed to absorb, transport and release latent heat collected from the air in your home. This is why an air conditioner doesn't so much "cool" the air as reduces indoor temperatures by "removing" existing heat from the air. Over time, dirt and debris can block air from flowing through the coils, making it much harder to absorb and expel latent heat. Excess frost build-up can also block air flow and reduce A/C performance.
A clogged coil can cause the A/C to run constantly, so it's a good idea to regularly check both evaporator and condenser coils for signs of dirt and debris, as well as mold and mildew. Cleaning the coils only takes a few minutes with a soft bristle brush and some mild detergent. However, take care to avoid damaging the fragile aluminum fins lining the coils during cleaning.
#3: Malfunctioning or Improperly Set Thermostat
If your thermostat is on the fritz, it may cause odd behavior in your A/C system. If you suspect a bad thermostat to be behind your A/C system's constant operation, it should be checked out before replacing it with a brand-new thermostat.
Your A/C system may also run constantly if you have the thermostat set to an abnormally low temperature, especially if there is a significant temperature difference between your home and the outdoors. In this case, the A/C system will continue to run in an attempt to reach an impossibly low temperature set point. Raising your thermostat to a more reasonable temperature can easily solve this issue.
#4: Low Refrigerant Charge
Your A/C system depends on a certain amount of refrigerant circulating throughout the unit. If there isn't enough refrigerant available, your A/C system won't be able to cool your home properly. A low refrigerant charge can also cause long-term damage to the compressor and other components.
Keep in mind that refrigerant isn't designed to "go away" over time. The only reason for refrigerant levels to drop is if there are one or more leaks somewhere within the A/C unit. If you suspect a refrigerant leak, you should have your HVAC contractor pinpoint the source of the leak and take steps to repair it. It can be potentially dangerous to check refrigerant levels on your own, plus your HVAC contractor will have proper tools and training to perform this task.
#5: Undersized A/C Unit
Whenever a new A/C unit is installed in your home, it's up to your HVAC contractor to make sure it's not too big or too small, but just the right size to cool your home efficiently and effectively. For example, an undersized A/C unit with a thermostat set to 72 degrees Fahrenheit and a current temperature of 78 degrees might not have the cooling performance to reach the thermostat set point. As a result, your A/C could run for hours on end in a futile attempt to bring the indoor temperature to your desired set point.
Recent renovations involving changes to your home's size and room layout can affect how your current A/C system performs. After an intensive renovation, it's important to have an HVAC contractor from a company like C B Lucas Heating & Air Conditioning reevaluate your home's cooling and heating needs.