Why is your air conditioner not cooling?

Key points

• Repairing an air conditioner costs between $100 and $600, depending on the issue.

• A refrigerant leak is one of the most common AC problems and should be treated by a professional as soon as possible.

• Routine maintenance, such as checking and replacing air filters, helps avoid AC malfunctions.

An air conditioner that is not cooling in the dead of summer is a homeowner’s nightmare. Precisely why your air conditioner is not cooling can be due to a range of problems. 

“Most typical issues during the summer are a result of dirty air filters,” said Marco Radocaj, owner of Balance HVAC in Vero Beach, Florida. This is a relatively easy fix, as you can replace clogged filters by yourself without calling in an expert.

As heat waves roll in, summer indoor air temperatures can become uncomfortable or even downright dangerous. While it can be costly to fix an AC, its ability to cool down a home is invaluable.

Repairing an air conditioner costs anywhere between $100 and $600, depending on the exact dilemma, said the experts we interviewed. At the same time, AC or HVAC technicians typically charge between $75 to $125 per hour to visit your home, as diagnostic tests can cost as much as $100 to determine the problem.

The type of AC unit itself can play a role in the cost. The different types include central air conditioning, which uses a system of air ducts — or ductwork — to send cool air throughout your home. Window air conditioners and portable AC units can cool a single room and are much less expensive to replace.

Here is a breakdown to help you handle an air conditioner that is not cooling.

Why is your AC running but not cooling?

You turned on the AC unit, but it’s not blowing cold air — or if it is, it isn’t very cold.

While this is frustrating, you can try to determine the problem yourself, which will help you prepare before talking to HVAC technicians. Below are some common causes of AC malfunctions and how to identify them.

Refrigerant 

Refrigerant is a fluid running through an air conditioner. If your AC isn’t running, the problem could be low refrigerant, which arises from a refrigerant leak. You’ll notice longer run times if this is the case. 

“Next, you would notice that the thermostat is not able to maintain temperature during the hotter times of the day,” said Radocaj. 

To determine if this is the case, check if warm air is coming from the AC registers. “The air should not be cool, but rather cold air,” he said. Also, look for ice forming on the larger of the two refrigerant lines. “You may notice a gurgling noise coming from the air handler or furnace,” Radocaj continued. This indicates there isn’t enough refringent running through the system.

HVAC systems are designed to be sealed systems, and you should never lose refrigerant unless you have a leak in the system.

Guy Caldwell

When the problem is a refrigerant issue, call an AC or HVAC professional right away. Refrigerant as a material is unsafe due to its toxicity and flammability. 

“HVAC systems are designed to be sealed systems, and you should never lose refrigerant unless you have a leak in the system,” said Guy Caldwell, HVAC Master Instructor at The Refrigeration School in Phoenix.  

If this happens, it’s vital for a licensed professional to address the leak and add appropriate refrigerant levels back in.

Thermostat

Are you having trouble engaging with the thermostat setting? In other words, is it switching on and off? If so, the problem could be a power issue. The thermostat is a device that regulates temperatures, and it needs batteries to run.

You can take a few troubleshooting steps to check for potential power issues. “First, make sure your thermostat has fresh batteries and replace them if necessary,” Caldwell said.

Next, turn off the AC/heat and turn on only the fan, at which point you should hear the fan running. “If you hear the fan, this indicates that the control voltage is present, and your thermostat is at least partially working,” he continued. In this case, there must be something else wrong with your air conditioning system.

Compressor

An AC compressor circulates refrigerant in an AC system. Many things could impact a compressor, making it a reason your AC isn’t working.

Compressors are great communicators when it comes to letting the homeowner know if there’s an issue. 

Marco Radocaj

To determine if this is the problem, start by listening. “Compressors are great communicators when it comes to letting the homeowner know if there’s an issue,” Radocaj said. “They make loud growling type noises.” 

Another thing to listen for is whether the compressor is too quiet. This would indicate that only the outside fan is running and not the compressor.

Evaporator coils

Evaporator coils are a big piece of your air conditioner system and work by removing heat from air. They can have all types of issues, but leaking refrigerant and airflow restrictions are common reasons for AC failure.

“Both would result in the coil starting to freeze,” Radocaj said. To diagnose this problem, check the larger of the two refrigerant lines, but this can be a big task. “The evaporator coil is enclosed within the system, and it is nearly impossible to physically see,” Caldwell said. So, call a professional to identify and then treat this problem.

Should you turn off an AC that’s not cooling?

Yes, if the air conditioner is not cooling, turn it off and call a technician. Keeping an air conditioner running while it struggles to start could result in overheating the AC compressor and causing further damage.

“If an AC system has been running under duress, it will likely need time to cool off or thaw out before it can be worked on, leading to more service visits,” Radocaj said. 

Leave windows cracked open to help cool things down in the house until the technician arrives and the AC is fixed.

How do you fix an AC that isn’t blowing cool air?

There’s a quick DIY for fixing an AC — change the air filter. “When the filters become dirty and clogged with dust, they block the system’s airflow,” Caldwell said. “If the filter is significantly dirty and restricts airflow, it may cause frozen evaporator coils.” 

Air filters can be purchased at your local hardware store. For all other AC issues, our experts agreed: Call a professional.

How much does it cost to fix an AC that is not cooling?

Typically, a service call and a diagnostic test performed by a technician cost between $100 and $130. Then, fixing any of the AC components can range from $100 to $600, depending on the problem.

Complex repairs involving multiple parts of the AC system can cost thousands of dollars. These are hard to provide cost estimates for, as they depend on the combo of parts and labor.

What’s next?

A broken air conditioner is not something to overlook. “AC systems do not self-correct and often running under duress leads to more problems,” Radocaj said. “Which means more expensive AC repairs.” 

Having an AC in working order may lower your overall energy bills, since the AC won’t be on while struggling to cool down a home, said the experts.

You can do your part to avoid AC malfunctions by checking the air filters for dust buildup. “The most important thing for homeowners to do is to regularly change the filter and keep the outside coil clear of debris to allow for proper airflow,” Caldwell said. Not to mention, swapping out air filters can improve the general air quality of your home.

The cost of fixing or replacing an HVAC can be pricey. But the good news is many companies offer service plans. “These provide discounts on repairs and service if annual maintenance is performed,” Caldwell added. “Additionally, there may be warranties included with new installations.” Ask your installer for information on how to set up these warranties. Look into home warranties, as some provide HVAC coverage.

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