Why Does My AC Keep Running?

With the hot summer sun beating down, the last thing you want to worry about is your air conditioner malfunctioning, but if it’s running constantly without cooling your house, there’s something wrong. A new air conditioner install that behaves underwhelmingly may be due to an undersized unit, but even normally reliable units can fail from time to time.

Simple Maintenance May Cure Constant Running

There are several causes of constantly running air conditioners. Luckily, a homeowner can handle most of them. Often, it’s just a case of overlooked maintenance that causes a unit to run constantly, so before you call your local air conditioner professional, check these items:

Air Filters. An air conditioner can only cool rooms effectively if it has plenty of air to condition. If your air filter is dirty, it limits the amount of air flow available to your unit. Check your filter once a month and change it whenever you notice it’s becoming difficult to see through. (Just because some filters can last three months doesn’t mean they all will under all conditions.)

Caulk and Insulation. A poorly insulated house allows a lot of hot air to penetrate the living area. Stop those leaks by caulking around trim, replacing door sweeps and adding attic insulation. If you’ve already caulked and insulated, check for breaches in your defenses — sometimes caulk can peel off or dry up, and insulation can become displaced by furry attic visitors.

Condenser. Your outside unit, also known as your condenser unit, needs plenty of air circulation to work at its best. When it’s clogged with vegetation or debris, it can’t get enough air to dispose of your indoor heat. Dust and dirt can also clog the tiny fins, so make sure you clean your unit regularly with a garden hose to remove these fine particles.

Ductwork. Loose ductwork can cause your air conditioner to run constantly, especially if multiple sections are leaking cool air. Instead of that air coming out of your vents at a nice, crisp temperature, it’s mixing with the air in your crawlspace, basement or attic and blowing out lukewarm. Air that’s not completely conditioned isn’t cool enough to bring your home’s temperature down sufficiently.

Thermostat Battery. Once in a while, the problem lies with your thermostat. A low battery can make it hard for your thermostat to function properly. Replace the batteries before you call a professional, and check to see if there’s a temperature setting tha will let your outside unit turn off on its own.

Time to Call In the Professionals

Once you’ve looked over the simple stuff, it’s time to call in a pro. Although complete failure isn’t common, older air conditioner units or those that might have been accidentally injured can develop problems that require a service call. When your air conditioning expert comes out to check your unit, he may find one of these problems:

Condenser Malfunction. Many parts in your condenser can fail, causing the process that cools the air to be interrupted. From the sensor that detects when the thermostat needs the unit to shut off to the valves and fans inside, your condenser is a complicated machine that needs servicing from time to time.

Dirty Evaporator Coil. It’s buried deep inside your furnace or air handler, but that doesn’t protect your evaporator coil from dirt. Over time, your evaporator coil can collect lots of muck, making it harder and harder for air passing through to be cooled to the proper temperature. Just as with a lack of airflow or leaky ducts, air that isn’t cool enough when re-entering your living space is going to keep your air conditioner running. Sometimes you can clean your evaporator coil yourself, but they’re often difficult to reach and require a trained technician.

Refrigerant Leaks. A slow leak in your refrigerant line makes it hard for your air conditioner to function properly. Without enough refrigerant to cool the air that’s passing through the evaporator coil, your air conditioner will constantly pump air that’s too warm into your home. It’s going to keep trying to cool things down, though, until your air conditioner has enough refrigerant to do its job again.

What if My Air Conditioner Tends to Run Constantly at Certain Times?

Sometimes, you’ll notice your air conditioner is running constantly, but only during the hottest part of the summer. When this happens, it’s likely because your unit literally can’t keep up with the outside heat. You can help it work better by installing a shade over the unit and/or planting a tree or series of bushes to help block the hot sun. (But don’t plant anything too close to the unit or you’ll shut down air flow.) You can also move the unit to the shadiest side of your home. You’ll be surprised how much better your unit works when it’s not fighting both indoor and outdoor heat.