Air Conditioner Running But Not Lowering Temperature – 11 Causes & Solutions

Picture this: you just arrived home after a long day of hard work but found that your house was sweltering even though your air conditioner was still running. 

How can that be? How to fix it? 

If you come across the same problem, don’t be agitated. I’ll go over all of the common causes of an air conditioner running but not lowering the temperature, as well as any possible solutions.any.

So, without further ado. Let’s get started!

1. Incorrect thermostat settings

wrong thermostat setting

Anyone can make mistakes. Perhaps the reason why your air conditioner is running but not cooling is that you set your thermostat incorrectly. 

For example, you may have turned on the heat or fan modes, which will not lower the temperature. Or you may have set the temperature too high.


Take a look at the settings of your thermostat and adjust it. 

2. Malfunctioning thermostat

Sometimes, the thermostat can fail and not be able to send the correct signal to your air conditioner. This could be due to dying batteries or defective wiring.

When this occurs, your AC may not cool your house below 75, even if you have set it at 70. 


The first thing you need to do is change the batteries. If this solution doesn’t work, you should call a pro to repair or replace the thermostat.

3. Dirty air filters

dirty ac air filter

Air filters are the least expensive HVAC component when compared to other components. However, it is the most likely to cause problems.

Air filters are in charge of capturing particles in the air, which is great. However, if you do not commit to regular cleaning, it will eventually become clogged. This will obstruct airflow, resulting in the evaporator coil freezing and the fan motor overheating.

These issues will reduce the cooling effect of your air conditioner, but more often than not, your machine will keep running.


Fortunately, air filters are easy to clean. All you need to do is simply remove, wash, dry, and reinsert it.

Depending on the system, your living conditioner, and the type of filter, you may need to clean the filter every three months. Perhaps less, perhaps more.

4. Blocked condenser

The condenser is exposed to the elements, meaning that debris, like twigs and feathers, can get inside accidentally.

When this occurs,  the heat transfer process of the condenser will be obstructed. Since the heat removed by your AC can’t be dispersed outside, the cooling performance will decrease.

In other words, your air conditioner will be running but will be unable to lower the temperature.


Clean around the outside of the outdoor unit, remove the top grate and clean the inside.

5. Refrigerant leak

By converting refrigerant from liquid to gas, air conditioners remove heat and humidity. When the refrigerant level drops, the evaporator coil freezes, and the blower and compressor overheat, resulting in less cooling.

Fortunately, the refrigerant level does not change under normal conditions. If you notice the refrigerant level dropping – for example, if you hear a hissing noise from your air conditioner – there is most likely a refrigerant leak.


Even if you can locate the leak, it is not something you can do yourself. Because refrigerant is a toxic chemical, it can only be repaired and recharged by certified professionals.

6. Defective blower 

We already know that a clogged filter can prevent your air conditioner from lowering the temperature, but it is not the only culprit.

When the blower or the blower motor fails, it loses its ability to draw adequate air, reducing the cooling in your home or room.


Check out the blower. If it’s caked with dust and dirt, you can try cleaning it to see if the problem goes away. Otherwise, you should hire a professional to repair or replace it.

7. Leaky ducts

If you are a central air conditioning system owner, ducts are another place you should examine.

If cracks or holes exist in the ducts, the cooled air will get into additional spaces, such as the attic or crawl space, reducing the cooling effect in your living spaces. 


If you are one of those who can locate the leaks, you can try to fix them yourself. However, a technician may help you to discover more potential issues. 

8. Undersized unit

Even if you have closed all the doors and windows, the heat from outside can still enter your home. That is why if you turn off your air conditioner for several hours, your house will become hot again.

When the air conditioner is too small for your home or room, the cooling is offset by heat entering the space, and the room temperature does not drop significantly.


To determine whether your air conditioner is undersized, contact a local contractor and request a manual J calculation. If so, it will necessitate the purchase of a larger unit.

9. It is too hot or cold outside 

cold outside

An air conditioner can’t function well when it is cold outside, nor does it work when the outside temperature is over 100 degrees.

When the temperature falls below a certain threshold, the lubricant thickens and the evaporator coil freezes. When the temperature is too high, the compressor will work at full capacity and eventually overheat.

As a result, your air conditioner will run but will not effectively cool your home.


Close the curtain to try to keep the heat out. Another option is to only run your air conditioner at night.

10. Hot and cold spots due to poor ductwork design

If you recently moved into a resold apartment, improper ductwork design could be the cause of your AC running but not cooling.

As a result, the cool air will be unable to disperse, resulting in hot and cold spots throughout the house. That is, some of your rooms can reach the desired temperature while others cannot.


Unfortunately, you should leave it to a pro. They will check the design of your system and make the adjustment.

11. Your air conditioner needs a replacement 

If none of the solutions mentioned above work, perhaps it is a signal that your air conditioner has reached the end of its life. 

Do you know how long your air conditioner has been running? If it has been more than ten years, chances are its efficiency has decreased due to mechanical wear and tear, and it can no longer lower the temperature as effectively as it once did.


It is time to replace your air conditioner! I understand that it is more expensive up front, but it will save you more money on electricity bills because units are much more advanced these days.


If you are wondering why your AC is running but not lowering the temperature, you have likely found the answers in this post. 

Wrong thermostat settings could be the culprit, whereas a dirty filter and condenser could also be to blame. Refrigerant leaks and leak ducts can also cause the problem.

If you want to prevent it from happening again, your best bet is to clean and maintain your machine on a regular basis.

About The Author

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested dozens of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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