Why is My Air Conditioner Freezing Up?

Your air conditioner just doesn’t seem to work as well as it used to operate. Warm air and extra electrical costs are making you wonder if the system has a problem. Open up the door to your interior AC unit, and you might encounter a frozen wonderland. A frozen AC unit is a serious condition that must be evaluated at once. Turn off the system, and take a good look at these components that might be malfunctioning.


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Low or Leaking Refrigerant

The refrigerant is the substance that makes it possible for the AC system to operate. It converts and moves hot air from the home while leaving cool breezes in its wake. Refrigerant runs through lines that snake through the structure, such as between the interior and exterior units. Although the lines are constructed with durable materials, they can leak over time and cause a frozen system. The refrigerant may leak significant volumes and should be evaluated by a professional. Leaks should always be repaired by the experts so that all hazardous waste is properly treated.

Neglected Air Filter

One of the most basic parts to your AC system is the air filter. As the system comes online, it draws air in through a vent. The incoming air moves through the filter where tiny particles are quickly captured. This process protects the home and its residents by removing most particulates from the circulating air. Cleaning the air filter must be a priority because a dirty or blocked part will cause a frozen AC. When air can’t move over the interior parts, their cooling process backfires and freezes up the components.

clogged air filter

Faulty Thermostats

A thermostat that’s malfunctioning can definitely contribute to a frozen AC unit. This situation occurs when the thermostat continues to run the system. The home may have reached the desired setting, but the thermostat doesn’t recognize this fact. The system continues to work feverishly, which leads to frozen AC parts. Replace or repair the thermostat to see a change in the operation. With the system running at a normal pace, the frozen parts will defrost in little time.


Man fixing thermostat

Dirty Evaporator Coil

The evaporator resides in the interior unit. It’s a key player in converting hot air to cool breezes. Because this unit is hidden away in most homes, it can get dirty. Grease and debris accumulate on the evaporator coils, which leads to poor conversion functions. Skilled technicians can clean the coil to help regain the required airflow needed.


Dirty evaporator coil

Improper Outside Air Temperature

When you live in a region that’s prone to hot temperatures, you may have your AC on for most of the year. Dropping outside temperatures, however, can make your AC freeze up. Most AC models can operate when the temperatures are higher than 62 degrees Fahrenheit. If the temperature drops below this threshold, the AC system starts to malfunction. Pressure within the AC becomes too unstable, which leads to frozen parts. Shut off the AC entirely if the outside temperature is very cool.

Air conditioner unit at night

Blower Fan Failure

Within the interior unit, there’s a blower fan that continually moves the air into the system. A malfunctioning blower means that the air is suddenly stagnant. There’s no steady way to move the air fast enough into the system. The resulting scenario is a frozen AC. Check the blower fan to confirm it is running. If it is not running it check for any tripped breakers.

Kinked Lines

Low or leaking refrigerant leads to a frozen AC unit, but so does kinked lines. Those refrigerant lines that stretch between the interior and exterior units may become kinked over time, such as during a remodel or other service project. The refrigerant can’t flow, which freezes the AC components. Resolving a kinked-line issue so that the refrigerant flows correctly will require a trained expert to repair.

Blocked Vents

As you decorate and fill the home with personal belongings, it’s easy to overlook the AC vents that are along ceilings and walls. Placing a cabinet or other object in front of the vents is commonplace for some residents. This practice, however, creates AC problems. These exhaust vents cannot move the cooled air out of the AC components so it backs up to the interior unit. As a result, the AC freezes up. Take a look around your home, and verify if any vents are covered. Rearrange the furniture, and you’ll see a difference in your AC’s operation.

Blocked Drainage Lines

Condensation naturally occurs during the AC process. Most homes have a drainage or piping system that moves the moisture out of the area. These conduits can become blocked over time, however. Clogged lines mean that water cannot leave the area so it backs up to the AC components. As a result, the water freezes and creates icy conditions across the unit. Unclog the lines so that the water can move efficiently away from the AC unit.

You’re perfectly capable of dealing with basic AC maintenance, but a professional’s help may be warranted at times. Ideally, you should get your AC system checked twice a year for a system evaluation. We can repair minor issues before they become big problems. Suggestions about upgrades might be in the cards too. You’ll have a well-maintained system that keeps you comfortable throughout the year.

Real Reviews

"So glad I called back when my A/C still wasn't actually cooling my house. I'd had RightNowAir check it out on May 2, but "all specs were in line" per that tech. This time I requested a tech a bit... Read More"

CarolAnn | Las Vegas, NV

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