AC Constantly Running? Here Are 9 Likely Reasons Why

Your air conditioner is built to work long hours, which is good news during the dog days of summer. But if your AC is constantly running even when you don’t have the thermostat set for it to operate, there could be problems afoot. Some of these issues are easy DIY fixes, while others require a call to your local AC repair company. As always, be smart when it comes to handling any electrical connections, and stay away from refrigerant fluid—it’s toxic if inhaled.

The Components Are Dirty

All major home appliances must be kept free of dust and dirt to allow for peak performance. If your AC is running continuously, it could be because you've got a dirty condenser, coils, fan, or filter, for starters. 

Be sure to replace your AC filter at least once per season, but switch to once monthly if you’ve got pets or someone in your home smokes. If your AC condenser unit is near a high-traffic area in your yard, it could be filled with grass clippings and other yard debris. Safely remove any blockages that you can because dirty components could also lead to frozen evaporator coils, which will cause your AC to malfunction. 

Refrigerant Levels Are Low

To work properly, your AC must maintain a certain amount of refrigerant. If there's a refrigerant leak or otherwise not enough refrigerant in the system, it can’t do its job—but it'll keep trying for hours and hours and hours because that’s what machines do. 

Don’t attempt to fix this problem on your own because refrigerant is dangerous to work with, potentially causing skin irritation, vomiting, difficulty breathing, and other adverse side effects, according to Mount Sinai.  

The Fan Limit Switch Is Stuck

If the fan is whirring even when the AC isn’t on, it could be that the fan limit switch is stuck. You can find the switch near the blower fan, but it’s difficult to spot if you don’t already know your way around AC components. If you’re unsure about how to reset it, call in a local AC repair person to do it for you.

There Are Issues With the Connections

An AC unit has various wires and electrical connections that can malfunction or become disconnected, causing an AC to keep running. Be safe and call a local AC repair person to troubleshoot this electrical problem instead of trying to DIY.

You Need a New Thermostat

Did you know that a thermostat lasts 10 years on average? During that decade of use, the sensors can get pretty dirty, which doesn't bode well for their ability to determine the temperature of a room. Wires and other connections could also get loose, which means the AC and the thermostat won't sync up. 

The Ducts Are Blocked

There may be an obstruction in your ductwork, or the dampers in your vents may be partially closed. Either way, run a check while the AC is on. If you don’t feel a cold blast through all of the vents in your home, it's time to hire a pro to clean your ductwork.

The AC Is Too Small for the Space

If it doesn’t have enough BTUs to cool the space, your AC will have to work that much harder. Even after running for hours on end, your home still might not feel cool enough. It's important to consult a professional HVAC installer to determine what size AC unit you need to cool your home effectively. 

Your System Is Too Old

There’s a natural end of life for appliances whether we like it or not. If your AC has been working tirelessly for many seasons on end but is starting to show signs of trouble, it could be time for a new system. Start making replacement plans if your unit is 10 years old or more. 

User Error

Did you happen to set your AC to “on” when you meant “auto”? If you have a new thermostat, take time to get to know the user manual so personal error doesn’t get in the way of your AC’s operation.

When to Call a Pro

If it’s summertime and your AC is acting up, it’s a good idea to hire an HVAC repair company. It’s peak season for those pros, so unless you’ve got emergency service as part of your appliance or home warranty plan, you might have to wait a bit for someone to arrive on your doorstep.

That said, you can replace the air filter in the meantime, clean components, and install a new thermostat if yours is past its prime. Be safe and refrain from touching any electrical connections or air conditioner refrigerant.