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

As someone who has an air conditioner at home, you’re probably aware of how big its energy consumption is. So even if you need the entire house to remain cool the whole day, having the AC running the whole time isn’t a practical option.

Most air conditioners’ settings can be adjusted, so they switch OFF automatically once a certain temperature has been reached. This can be your AC’s way of helping you save electricity and lowering your utility bills. However, there are times when your AC may not work exactly as you need it to.

Your air conditioner may keep running even after the set temperature has been reached. If this happens, don’t panic. Although it would explain your increasing electricity bill lately, some reasons it’s happening don’t require much fixing. What’s important is you immediately take action and not allow the problem to persist as it may lead to other major issues later.

Continue reading to learn about the reasons for this issue on your AC and what you can do to address it.

Reasons Why an Air Conditioner Keeps Running After Reaching The Set Temperature

While you shouldn’t be immediately concerned when this happens, you may be ignoring a serious problem if you don’t do anything. Knowing why your AC keeps running after reaching the set temperature is essential as it helps you determine how to fix it. 

Reason 1: Clogged or dirty air filter

No matter what issue your air conditioner has, one of the first things you need to check. A clogged air filter leads to airflow problems which prevent your AC from functioning correctly.

Luckily, cleaning your air filters should remove whatever caused them to clog. This should be done regularly to prevent any dirt or debris from building up and ensure everyone in the house isn’t breathing dirty air. Watch this video to learn how.

If you think your air filter already needs to be replaced, you should be able to find one here. Just make sure to get one that’s compatible with your AC.

Reason 2: Restrictive air filter

If you replaced your AC’s air filter recently, it’s possible that you got one that’s too restrictive. Your new air filter may be restricting the airflow too much and is making your AC work harder than normal.

Purchase an air filter with a low Minimum Efficiency Reporting Values (MERV) rating to fix the issue

Reason 3: Dirty evaporator and condenser coils

Dirty evaporator and condenser coils

When your air conditioner’s coils are already covered in dirt, it significantly affects your AC’s ability to cool the entire area. In addition, the presence of built-up dust and debris can make your AC run slower – thus taking longer to reach your desired temperature.

The obvious solution would be to clean your air conditioner’s coils. It may be hard at first, but it should eventually become easier the more you do it. For instructions and more details, click here. You may also check out our guide for the best AC coil cleaners available.

Reason 4: Frozen evaporator coil

A sign that the evaporator coil has frozen is when your air conditioner produces warm air. A frozen evaporator coil is usually a result of other issues such as leaks and low refrigerant levels. Determining the reason for freezing should be done by a professional.

Nonetheless, it’s still possible to unfreeze the evaporator coil yourself by doing the following:

  • Switch OFF and don’t use the AC for 24 hours to let the frozen evaporator coil thaw
  • If it looks dirty, clean the evaporator coil
  • Replace the air filters if they are covered in dirt.

That said, getting help from a technician would be best as you could be dealing with a damaged evaporator coil.

Reason 5: Leaking ducts

Air conditioner ducts are responsible for proper air transportation and circulation. When there is leaking on the ducts, your AC would need to run constantly to compensate for any cool air escaping through the leaks.

Sealing the leaks won’t be easy, given that some buildings have older ducting systems. This means you need to call an expert for help. Fixing them yourself may be a lot cheaper, but your inexperience may cost you more on repairs later.

Reason 6: Defective thermostat

Air conditioners have a thermostat that controls the temperature of the air being emitted. Unfortunately, a faulty thermostat won’t be able to sense the current temperature in the room. This causes the AC to keep running even after the set temperature is reached.

Before you even consider replacing it, you need to confirm if the thermostat is the actual source of the problem. Either way, you will need the assistance of a technician.

Reason 7: Decreased refrigerant level

Decreased refrigerant level

The chemical substance that allows your air conditioner to produce cold air is the refrigerant. A low refrigerant charge may result from other underlying issues in the air conditioning system – particularly with the coils. Leaks or dirt in the coils could make your AC struggle to sustain a cool temperature.

For a quick fix, you can try cleaning the coils or sealing the leaks yourself. But getting help from a professional could help determine other issues that you may be unaware of. 

Reason 8: Blower motor and fan problems

Additional factors contributing to an inefficient air conditioning system are the blower motor’s inability to produce adequate air and the fans beginning to slow down.

This problem can be solved by adjusting the fan speed to your preference. If it’s still at slow speed, cleaning the fan blades might help since a layer of dirt may be what’s slowing it down. However, only an HVAC technician can determine if the motor and fan need to be replaced, so it’s best to give them a call.

Reason 9: Incorrectly-sized AC unit

Your air conditioning system’s capability to maintain a cold temperature can be altered if your space recently underwent renovation. This is probably because your AC’s power output or size isn’t enough to support your new layout fully.

To ensure that your AC unit is correctly-sized for your space, have an expert perform a load calculation. This process considers everything, including the size, design, circumstances, and other possible needs. Click here to know more about how air conditioners are sized.

Reason 10: Maintenance needed

Similar to your car and other home appliances, air conditioners need routine maintenance to ensure optimum performance during their entire lifetime. AC units should ideally undergo maintenance at least twice a year, during spring and early fall.

Your nearby HVAC expert will be responsible for doing maintenance work. This person will check for any defective or worn-out parts and recommend which ones need to be fixed or replaced. A well-maintained AC unit typically lasts longer and is safer for the whole family.

What Can You Do When Your Outside AC Unit Runs Constantly?

The most common reasons for a constantly running outside air conditioner unit are the following:

Here are a few things you can do to address this problem:

  • Clean your air filters as often as possible and replace them four times a year.
  • Ensure proper ventilation by opening the supply vents and checking if any grille vents are blocked.
  • Assess for the presence of leaks and frozen evaporator coils from time to time to prevent any refrigerant from leaking.
  • Remove any dirt or debris stuck on the condenser coils for better heat absorption.

Additionally, you can use the above reasons as your guide to check for other possible issues your outside AC unit might have. Also, there’s no shame in seeking help from HVAC experts as they might find problems with your unit that you never knew existed!

People Also Ask

How long should AC run after reaching temperature?

Typically, air conditioners should only be running for about 15 to 20 minutes after it has reached the set temperature. However, the duration may vary depending on the following factors:

  • Your AC’s overall condition
  • The size of your AC
  • The size and layout of your space
  • The temperature outside

Contact a reputable HVAC expert, and they will determine how long your AC cycle should be.

How do I know if my AC thermostat is terrible?

Below are telltale signs that your air conditioner’s thermostat is malfunctioning:

Before concluding that your AC has a defective thermostat, do the following:

  • Open the thermostat and sweep off any dust using a tiny paintbrush.
  • Check for any structural problems inside the thermostat, like loose screws or wirings.
  • Remove and replace the thermostat’s batteries as they might be worn out.
  • Try to see if the thermostat is in the correct location.

If none of the steps above work, have a technician check on your AC to confirm if it needs changing. Watch this video to get an idea of how professionals replace a thermostat on an AC.

How do I stop my AC from short cycling?

A short cycle happens when your air conditioner shuts OFF before reaching the set temperature. Short cycles are often a result of a defective thermostat. To prevent short cycles, you need to determine if your thermostat is still working correctly by following the abovementioned steps.

Short cycling can also happen due to reasons other than a bad thermostat. The noise your AC makes should tell you more.


It’s never a good sign when your air conditioner needs to run constantly to maintain the recommended temperature for your space. It will result in electricity bills that are higher, but it also puts your family’s health in danger.

Don’t hesitate to call your local HVAC technicians whenever this happens to you. They know exactly what they’re doing, and their expertise may save you some cash down the line!

Does your AC have a different problem? This article might be helpful.

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