Why Does My Air Conditioner Keep Running After It Has Reached the Set Temperature?

Are you tired of finding that your air conditioner keeps running even after it has reached its set temperature? Do you not know what causes this problem and how to solve it? 

Well, when an air conditioner keeps running, it can cause plenty of issues, ranging from continuous noise to huge electricity bills to internal damage. Now, this can certainly cause a lot of nuisance. 

So, to know the reasons why your AC keeps running and their respective solutions, read on!

How Long Should An Air Conditioner Run to Cool House?

It is necessary to know for how long an air conditioner should work to cool your entire house. 

Most of the time, an air conditioner takes around 15 to 20 minutes to cycle to cool the entire house. However, there are certain conditions here. 

Size of Air Conditioner

The size of the air conditioner is in accordance with your house’s size. 

You might want to know that if your air conditioner is too large compared to your house, then it can cool the entire area in less than a 10 minutes cycle. 

Yet, this is not a good thing as your AC won’t reduce the humidity in the air. Hence, make the house feel humid. Moreover, it can also get overworked too easily, which can lead to more repairing costs. 

Outdoor Temperature

Secondly, the temperature outside also affects the cooling power of your air conditioner. Keep in mind that if it is too hot or humid where you live, then it can take longer than a 15 to 20 minutes cycle to cool the entire house. 

So, depending on the above factors, you can determine how much time it will take your AC to cool your house. 

How Long Should Your AC Run a Day?

If you are wondering how long an AC should run on a day, you need to keep in mind that it is entirely dependent on some factors. These factors include: 

Temperature Outside

The temperature outside is a major factor for understanding how long to run an AC. For instance, during the hot summer days, it is preferable to run the AC throughout the day. 

Now, you may think that frequently turning it on or off is a good idea. However, it could also lead to a phenomenon known as ‘short cycling.’ This short cycling can 

affect the performance of your air conditioner and also lead to its wear and tear. 

On the other hand, during mild days, you can run a short 10 to 15 minutes cycle at a time to ensure that your house remains cool. 

Thermostat Setting

The thermostat setting also affects the duration your AC runs for. Keep in mind that if the setting on your thermostat is low, then you’ll have to keep your AC on for a longer period, especially during summers. 

However, if you try to adjust your thermostat settings, you can reduce the runtime of your AC accordingly. This can help you save up on energy and those expensive electricity bills. 

Air Conditioner’s Size

Your air conditioner’s size is a major factor in deciding how long to run your AC for. So, as mentioned above, if the air conditioner’s size is too huge compared to the house, it can cool the place in a shorter time (10 minutes cycle). Yet, it can increase the load on your AC. 

If the AC’s size is too small compared to the house, it will take more time (20 minutes cycle) to cool the place. Hence, in this case, you’ll have to keep it on for an extended amount of time. 

So, make sure that you have the correct size AC to prevent these problems. 

State and Efficiency of the AC

Another factor that affects the cooling power of your AC is its state and efficiency. 

If your AC is well-maintained and in an efficient condition, then you can keep it on for a less amount of time, whereas, for inefficient ones, it can take longer. 

Size of the Room

Lastly, the area of your house is also a deciding factor. 

So, if the area is too huge, then you’ll have to keep the AC for a longer duration, especially if it is a small AC. in this case, to reduce the wastage, try to cool only the rooms which you are using and for the rest, close the doors and windows. 

However, for smaller homes, you only need to keep the AC on for some time. 

How Long Should It Take to Cool a House From 80 to 72?

If you want to cool a house from 80 to 72 degrees, you also need to consider some of the above factors, like the outdoor temperature. 

Most of the time, it takes around 4 to 6 hours to cool a house from 80 to 72 degrees. So, keep this in mind and plan accordingly. 

10 Reasons Why Air Conditioner Keeps Running After It Has Reached the Set Temperature

Now, if your AC has a set temperature and still keeps running after that, you need to find the reason behind it. This will help in preventing the unnecessary wear and tear of your AC, along with high electricity usage. 

Given below are 10 of the most common reasons why your air conditioner keeps running: 

1. Evaporator Coil Is Too Dirty

One of the major reasons your air conditioner keeps running could be because the evaporator coil is too dirty

The role of an evaporator coil in an AC is to convert moisture into water. However, if humid air contains a lot of dirt and debris, it can get accumulated here. Hence, when the evaporator coil gets dirty, it will function extremely slowly and cause your air conditioning system to become slower. 


If you want to solve this issue, you can either call up a professional to clean the evaporator coil or do it yourself. 

To do it yourself, try following the below-mentioned steps:

  • In a spray bottle, add detergent and warm water. Then, mix them. 
  • Spray the solution onto the evaporator coils. 
  • Let the solution sit there for a few minutes to soak up the dirt and debris. 
  • Wipe away the solution using a cloth. 

Remember that you might still have to call up a professional if it gets too dirty or grimy. 

2. Evaporator Coil Has Frozen

A clear sign that the evaporator coil has frozen is when you can feel warm air coming out of the air conditioner, along with its continuous working. 


If your evaporator coil has frozen, then you need to know the cause to solve the problem. Some other steps that you can follow to de-freeze your evaporator coil include: 

  • Allow the frozen evaporator coil to thaw out completely for at least 24 hours. 
  • Clean the evaporator coil. Make sure the air filters are clean or replace them. 
  • Make sure that the evaporator coil doesn’t have any damage. In case it does, call up a technician. 
  • Ensure that the refrigerant levels are proper and not too low. If not, there’s the possibility of a leak. Try to call up a professional and get your system checked thoroughly. 

3. Air Filter is Clogged

Clogged air filters can pretty much cause a lot of problems, including this one. The reason is that when the air filters are clogged, there isn’t enough air flowing through the system. 

Hence, it will take longer for your AC to cool your house correctly, leading to its continuous functioning. 


You can easily change an air filter by purchasing a proper replacement. Then, making sure that it is facing the correct way. If you have a reusable air filter, remove it, vacuum the large particles, and then wash with a mild soap solution. 

However, if you want to avoid this situation, you may want to clean or change your air filter regularly. 

4. Air Filter is Too Restrictive

If you are using an air filter with a high MERV rating, it can get quite restrictive for your air conditioning system and reduce the airflow. Hence, this can also make your air conditioner run for long as it requires more time to cool the room. 


If you face this problem, you have to go for a new air filter with less MERV rating. (preferably between 8-11 for home or commercial use)

5. Leaks in Ducts

This problem is very common for those living in old houses or buildings having old ductwork. 

So, what happens here is that the cool air might escape due to the leaks found in the ducts. Hence, making your air conditioner work continuously for more air supply to keep your house cool. 


Leaky ducts are often tricky to fix as they require a lot of time and effort. Moreover, if you’re doing it yourself, the expense can reach around $100 to $500. So, it is a better option to call up a professional and let them diagnose the problem. 

6. Issues With Thermostat

Sometimes, even minor issues like thermostat problems can keep your air conditioner running even after the temperature is set. 

It is because if there’s any problem with the thermostat, it won’t know when to turn it off even though it is at the set temperature. 


Firstly, you need to check whether there’s an actual problem with the thermostat. If there is, then you need to replace it entirely. 

7. Low Refrigerant Charge

When there’s a low refrigerant charge, then also your AC will keep running. It could be because of some leaks present in the coil. Hence, this can cause your AC to work extra hard and cause issues. 


Try to find a reliable HVAC professional that can help in finding the leak and repairing it. If not, you can also make use of a freon leak repair kit for small leaks. Still, consider calling up a professional.  

8. Condenser Problems

If you have a dirty condenser, it can make your AC run even after reaching the set temperature, just like a dirty evaporator coil. 

Again, the accumulation of leaves, dust, dirt, and other debris can impede the airflow and make your unit function improperly. 


If you want to clean your condenser unit or coil, opt for a good condenser coil cleaner, and follow the instructions below: 

1. Inspect everything first, including the condenser coil and its area

2. Start cleaning the debris from the condenser unit using a coil brush 

3. Make sure you straighten out the coil fins properly

4. Then, make sure of a foaming condenser coil cleaner to clean the area

5. Lastly, wash away the foaming cleaner after 10 minutes 

9. Over or Undersized Unit

This point is applicable if you have recently renovated your house or changed the layout of it. Here, the problem could be in the unit itself as it might not be enough for the new area or layout. 


There’s no quick fix for this problem as you might have to call up a professional for the load calculation. They can help you by providing the best solution accordingly. 

10. Issues With Blower Motor or Fan

Your AC might keep on running if there’s an issue with the fan or blower motor. 

For instance, the blower motor might not be giving out the proper amount of air, or the fan is simply working too slow. 


In this case, you need to adjust the fan speed accordingly. If the fan blades are too dirty, consider cleaning them to see effective results. 

Final Thoughts

To conclude, ensure that you find out the issue with your air conditioner by checking out the above reasons and their respective solutions. 

It is important because if your air conditioner keeps running even after reaching the set temperature, it can lead to its damage!

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