Why Is My Air Conditioner Not Cooling?

If your air conditioner isn’t cooling properly, the issue could stem from something as simple as an incorrect thermostat setting or as complex as a refrigerant leak or failing compressor. Your system depends on several components working in sync, and when one fails, it can disrupt the entire cooling process.

Below, we break down the most common reasons an air conditioner stops cooling and what you can do to fix it.

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5 Reasons an Air Conditioner Stops Cooling

Depending on your central air system or your chosen air conditioner brand, many specific issues may prevent your air conditioner 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 mold spores, dust, and pollen. 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.

If there’s a leak in the refrigerant line, some of the fluid is lost during this cycle, which reduces the amount of cool air the system can produce. In these cases, a licensed technician will need to locate and repair the leak before recharging the system. This service can increase your freon costs, especially if your air conditioner uses an older refrigerant like R-22.

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. Replacing an evaporator coil will be expensive, so it is recommended that you keep your system routinely maintained.

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 returns all the absorbed heat to the compressor. The excess heat is then 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. At this point, you will likely need to incur the expense of installing a new AC compressor.

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Signs That Your AC Needs Repair

When your air conditioner isn’t working as it should, small warning signs can point to larger issues. Catching problems early helps prevent more serious and expensive repairs down the line. Look out for the following indicators:

• Foul odors: Burning or musty smells coming from vents may suggest mold growth, dirty components, or electrical problems.
• Insufficient cooling: If your AC is running but not cooling your home effectively, it could be due to a refrigerant leak, a failing compressor, or restricted airflow.
• Leaking moisture: Water pooling around the unit could indicate a clogged condensate drain or refrigerant leak, both of which require professional attention.
• Unusual noises: Grinding, banging, or squealing sounds may signal mechanical issues, such as a loose belt, broken motor, or failing bearings.
• Weak airflow: Poor airflow may be caused by a clogged filter, malfunctioning fan, or issues within your ductwork.

If you notice any of these warning signs, call a licensed HVAC technician before the issue worsens.

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How To Maintain Your Air Conditioner

Air conditioner repair costs range from $100–$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. Remove any noticeable debris lodged inside after turning off the unit and removing the top cover. Use gloves when reaching inside your unit to prevent cuts from sharp parts.

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.

First, ensure the unit is completely off to clean the evaporator coil. Then, locate your unit’s air handler in a closet or attic. Remove the air handler’s access panel and spray the 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.

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When To Call In a Professional HVAC Service

While simple maintenance tasks like changing filters or clearing outdoor debris can be done on your own, more complex issues should be handled by a licensed HVAC contractor. Here’s when to bring in the pros:

• A component has failed: If major parts like the condenser or evaporator coil stop working, they need expert attention. For example, replacing an AC condenser can cost around $2,500, and incorrect DIY repairs could lead to further damage.
• It’s time for an inspection: Schedule professional HVAC maintenance at least once a year. These checkups keep your system running efficiently and can catch minor problems before they become expensive breakdowns.
• You’re buying a new system: An HVAC technician can recommend the correct AC unit size for your home. A unit that is too small will run constantly, while one that is too large may cycle too frequently. Both scenarios reduce efficiency and can lead to premature wear.
• You’re facing an emergency: If your AC makes loud banging noises, emits a burning smell, or stops working entirely during a heatwave, call a technician right away. These could be signs of electrical issues or serious mechanical failure.
• Repair costs are climbing: Replacement may be the better investment if your air conditioner is more than 10 to 15 years old, and an AC repair costs more than half the price of a new system. A technician can assess whether it is worth repairing or replacing.
• You have a warranty: Check your system’s warranty terms before attempting any repairs. DIY fixes could void the coverage, leaving you responsible for the full repair costs.

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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 more frequently you clean 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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