AC Running Constantly & Won’t Turn Off At Set Temp (Causes)

Nothing beats an air conditioner in the dog days of summer. But if an AC is constantly running and won’t turn off at the set temperature, it may be a sign something is wrong with the unit, and repairs may be in order.

Why Won’t My AC Turn Off At The Set Temperature (Causes & Fixes)

If an air conditioner doesn’t stop running once it reaches the set temperature in the room, it can be a sign the unit is overexerted or malfunctioning. These issues can come from several different places.

AC Runs Constantly Due to Restricted Airflow

If you find yourself asking, “Why does my air conditioner keep running after it has reached the set temperature?” it is likely due to restricted airflow. According to research done by the Department of Energy, clogged or dirty filters lower an AC unit’s efficiency and increase power consumption by up to 15 percent.

If an AC keeps running after temp is reached, the first step is to check the air filter. For optimal AC, change your filters four times a year. This may need to be done more often if you have pets or severe allergies. If the filter in the air conditioner appears dirty or clogged, it should be replaced to increase airflow.

Following the air filter check, an examination of the supply vents is in order. Open all the vents in the home, even in rooms not currently occupied. Another way to increase airflow is to check for any blockage of vents. Curtains or furniture in the way of the airflow should be moved.

These tips should fix the majority of airflow issues. If airflow problems still exist, it may be time to call a local HVAC professional to service the device.

AC Runs Constantly Due to Low Refrigerant

If an AC does not shut off when the set temp is reached, it could be an issue of low or leaking refrigerant. According to the Department of Energy, an AC low on refrigerant is most likely undercharged at installation or has a refrigerant leak.

You can conduct a few tests to determine if the refrigerant is the source of an AC unit’s issues. Warm air coming out of the AC rather than cold air could be a sign the refrigerant is an issue. If the evaporator coils of the AC are frozen, it is a sign the refrigerant is leaking.

If an AC unit requires additional refrigerant, it is time to call an HVAC professional. They can assess the issue, fix any leaks, and add refrigerant to the unit. Doing so should fix the issue of an AC running constantly and not shutting off when the set temperature has been reached.

AC repairman

AC Runs Constantly Due to Dirty Condenser Coils

Over time, an air conditioner’s condenser coils can become dirty and less efficient. An AC unit relies on the condenser coils to absorb heat inside a house and expel the heat outside. Blocked or dirty condenser coils can prevent that process, leading to an AC that does not shut off when it reaches the set temperature.

The Department of Energy recommends checking the evaporator coils every year and cleaning them as needed. It also recommends keeping foliage back at least two feet to allow appropriate airflow. If you’re having a hard time cleaning the coils, it might be time to contact an HVAC professional in the area.

Related Article How to Clean AC Coils

How Long Should An AC Run After Reaching Set Temperature?

AC Units are designed to cool in intervals of 15-20 minutes before shutting off. When the temperature begins to rise again, the air conditioner will start again.

Once the desired temperature is reached, an AC unit should shut down within a few minutes if it is working properly. The air conditioner is designed to expel the last of the cold air from the ducts before shutting off to rest.

If an AC is running constantly and does not shut off when the set temperature is reached, it could be a sign of an issue with the unit or the thermostat.

What To Do If The AC Won’t Turn Off After Reaching The Set Temperature?

If the AC keeps running after the temp is reached, it is important not to panic. Sometimes, it is a quick fix, as simple as manually shutting off the AC. Setting the thermostat to a few degrees higher than the current temperature should power off the unit. If the AC is still running, there may be another issue.

AC owners can check the condenser for issues. If the problem is not immediately obvious, it is time to call an HVAC specialist. They can assist in solving any AC problem.

Why Is It Important the AC Turns Off At The Set Temperature?

AC units are designed to regularly shut off for several reasons. Shutting down allows the AC to rest, avoid excessive wear and tear, and extend an AC’s lifespan. That process saves money for a homeowner in the long run.

It is also vital for the AC to turn off regularly to save on cooling costs. A constantly running AC wastes not only energy but money through its inefficiency.

daikin air conditioner review

People Also Ask (FAQ)

The following are frequently asked questions related to AC temperature.

Should an air conditioner run 24/7?

No, an air conditioner is intended to shut off at regular intervals. Doing so prevents wear and tear and keeps cooling costs lower.

How long should my HVAC fan run per hour?

Most HVAC fans run in about 15-minute intervals. These intervals happen two to three times per hour, depending on the temperature outside.

What will it cost to have an HVAC technician fix this issue?

A typical service call can cost around $100. Repairing a refrigerant leak can cost from $200 to $1,500, depending on the severity of the issue.


If the AC is running constantly and does not shut off when the set temperature is reached, you should take action to fix the unit. Check the filters for any airflow problems. Then check for any issue with the refrigerant or condenser coils. And, when all else fails, call a local HVAC professional to fix the air conditioner.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.