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Why Is My Air Conditioner Not Cooling?

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Author Image Written by Brenda Woods Updated 02/02/2024

When turning down the thermostat, you expect the air conditioner to supply fresh, cold air. But like any mechanical system, your AC unit relies on many interactions between intricate parts to produce cool air. If one of these parts isn’t working, the entire system may fail.

Below are some common reasons why an air conditioner isn’t cooling your home and what you can do about it.

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HVAC Installation

Installation costs for common air conditioning units range from $500–$2,500.

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Depending on the repair, the typical cost ranges from $100–$2,000.

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5 Reasons an Air Conditioner Stops Cooling

Depending on your central air system or air conditioner brand, many specific issues may keep it from cooling properly. The following reasons are some of the most common.

1. The Thermostat Is Set Incorrectly

For the thermostat to be effective, you need to make sure that it’s on the correct setting. The thermostat should be set to “cool” or “auto” instead of simply “on.” “Auto” runs the air conditioner and circulates cool air as needed, whereas “on” runs the air conditioner even when cool air isn’t being produced.

2. You Have a Dirty Air Filter

An air conditioner filter traps harmful and irritating contaminants like dust, pollen, and mold spores. Over time and without proper cleaning, air filters can become clogged and prevent air from properly passing through. Additionally, when clogged air filters trap cool air inside the unit, the evaporator coil is at risk of freezing, which could restrict airflow.

3. There’s a Refrigerant Leak

The air handler, the interior part of your air conditioner, is home to the evaporator coil that’s responsible for cooling your home. The handler absorbs warm air through the evaporator coil and transforms it into a gaseous state. The result of this heat absorption is cool, dry air that is then pushed into the house through the unit’s blower and air ducts.

To keep the process continuous, the compressor puts the gas refrigerant under intense pressure, releasing excess heat outside and transforming the gaseous refrigerant back into a cool liquid with the help of the condenser. The evaporator coil can then create more cool air by starting the process over again.

When there’s a leak in the refrigerant line, some of the fluid is lost during its cyclical transformation process. This results in an inadequate amount of cool air being produced.

4. The Evaporator Coil Is Dirty and Freezes

The evaporator coil contains the refrigerant that cools your home. As mentioned, the coil absorbs heat from inside your home, pushing cool air to the blower and transforming the refrigerant into a gaseous state. If your evaporator coil is too dirty, this can reduce the amount of heat absorbed, causing the cold evaporator to freeze over and disrupt the cooling process.

An evaporator coil can also freeze due to a refrigerant leak. When refrigerant levels drop, so does the temperature which can freeze the entire evaporator coil.

5. The Air Conditioner Compressor Isn’t Working Properly

Your compressor pumps refrigerant from the outdoor unit to the indoor unit. As the liquid refrigerant moves into your home, it enters the evaporator where it absorbs your home’s heat and produces the airflow felt from your vents.

Once the refrigerant fully vaporizes, it brings all the absorbed heat back to the compressor. From there, the excess heat is transferred outside and the refrigerant returns to a liquid with the help of the condenser, starting the process all over again.

If the compressor breaks down, the refrigerant can’t undergo its eventual cooling process. This results in warm air being pumped throughout your home.

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How To Maintain Your Air Conditioner

Repairing an air conditioner can cost anywhere from $100 to more than $1,000. To avoid pricey repairs, it’s important to prioritize AC repair and maintenance. Fortunately, there are a few tasks you can tackle on your own.

Before performing any do-it-yourself (DIY) air conditioner maintenance, ensure that the unit is completely powered off. This can be done through the exterior shutoff box or your home’s breaker box.

Clean Your Outdoor Unit

The central air conditioner unit outside of your home includes the condenser and compressor. After turning off the unit and removing the top cover, remove any noticeable debris lodged inside. Use gloves when reaching inside your unit to prevent cuts from sharp parts.

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Clean the Evaporator Coil

You should clean the evaporator coil at least twice per year using a soft brush and a coil cleaner. This will help maintain evaporator coil efficiency and keep your unit operating smoothly.

To clean an evaporator coil, first ensure that the unit is completely off. Then, locate your unit’s air handler, usually situated in a closet or attic. Remove the air handler’s access panel and spray no-rinse coil cleaner directly onto the evaporator coil. Use a paintbrush to gently remove debris before replacing the access panel.

Change the Blower Filter

When a filter is clogged, cool air won’t reach your home. Change your blower filter at least twice a year to maintain cool, clean air throughout your home.

Read more5 Essential Steps for Window AC Upkeep


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When To Call In a Professional HVAC Service

With a little time and effort, you can maintain your cooling system through regular cleaning and maintenance. When it comes to mechanical breakdowns and technical questions, however, maintenance and repairs are best left to the professionals. Here’s when to call an HVAC technician:

If a specific air conditioner part breaks down—When the condenser fails or the evaporator coil freezes over, these parts must be repaired by an expert.
For routine inspections—Your air conditioning system should receive inspections by an HVAC professional at least once a year. This will ensure that the unit is working properly and help to identify any problems or premature wear and tear.
When looking to purchase a new unit—If you’re looking to purchase a new AC system, have a professional come by to identify the best unit size for your home. Too small of a unit will constantly run and be overworked, while too large of a unit can be subject to premature wear and tear from the system cycling on and off. Your home needs a proper-sized unit that runs for the correct amount of time to comfortably cool your home.

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FAQ About Air Conditioners Not Cooling

Can I do air conditioner maintenance myself?

With proper guidance, you can perform routine air conditioner maintenance yourself. Always turn your AC unit off before doing any work, as failing to do so is likely to cause serious injuries. If your air conditioner is having issues, it’s best to call in a professional.

How often should I clean my air conditioner filter?

Try to clean your air conditioner filter at least once every three months. The greater the frequency of cleaning it, the better your house’s air quality will be.

When do I need to call a professional to fix my air conditioner?

It’s best to call a professional to fix your air conditioner whenever it starts having issues. Their expertise in dealing with a complicated piece of equipment such as an air conditioner is likely worth it versus performing potentially dangerous DIY work.


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