Why Is My Air Conditioner Freezing Up?

Frozen Air Conditioner

We regularly rely on our air conditioners to combat the heat, so it’s surprising to most homeowners to hear that the unit can freeze up; it sounds almost impossible for your unit to freeze when it’s above 70 degrees outside. Unfortunately, air conditioners can freeze in just about any temperature and require professional AC repair, and it’s more likely to occur in the heat of the summer.

Below, HVAC experts from Blue National HVAC will explain three reasons why your air conditioner might freeze, solutions for each issue, and how to prevent your equipment from freezing up altogether.

Three Reasons That Cause Air Conditioners To Freeze Up

Before we dive into what causes these sometimes costly issues, it’s helpful to understand what it means for an air conditioner to freeze. The evaporator coils in your air conditioner contain evaporated refrigerant, which naturally pulls energy, or heat, out of the surrounding air. The blower fan pushes recirculated air from your house over the evaporator coil, which then absorbs heat and cools the air.

Inside the evaporator coil, if the refrigerant is allowed to expand too much, it cools the air more than intended and causes the equipment around the coil to freeze. Ice will often form around the evaporator coil, leaving you with a malfunctioning air conditioner that is probably blowing hot air instead of cool, comfortable air.

Now that you understand a bit about how an air conditioner freezes, let’s discuss why this happens.

1. Dirty Filters

Unfortunately, something as simple as dirty filters can cause your air conditioner to freeze up. When airflow is blocked by dust or dirt in the filters, humidity in the air can accumulate around the evaporator coil and begin to freeze. The more your equipment works to cool the interior of your home with blocked filters, the more humidity will condense and freeze in your unit.

Solution/How To Fix

The easiest way to fix a frozen air conditioner caused by dirty filters is to clean the filters and returns and ensure that airflow through your vents is unimpeded. It’s best to have a professional inspect your equipment for significant damage, as running an AC when it’s frozen can have a substantial impact on most of the components.

2. Refrigerant Leak

A refrigerant leak is often one of the most expensive issues that cause your AC to freeze up because it commonly requires system replacement. When the refrigerant leaks from a kinked hose or cracked coil, it expands too much and freezes the air and any moisture around it. Eventually, your air conditioner will run out of refrigerant and won’t function at all.

repair man checking in on the function of an ac unit

Solution/How To Fix

Refrigerant leaks usually can’t be permanently fixed. The refrigerant can be refilled, but this is only a temporary solution in most cases, as it will continue to leak. Replacing your outdoor equipment is likely necessary, but a refrigerant refill could act as a patch to get you through the rest of the summer.

3. Damaged Blowers, Fans, or Ducts

In addition to clogged filters, anything that reduces airflow through your system will likely lead to a frozen air conditioner. The most common culprits other than fans or blocked vents and returns include a damaged blower motor, insufficient fan speed, or damage to your duct system. All of these problems reduce airflow over your evaporator coil and allow the surrounding air to become supercooled, leaving ice to form on the components.

Solution/How To Fix

The solution to this issue will depend on the underlying problem. A damaged blower motor will need to be replaced in most cases. A fan might be receiving low voltage for some reason and could just need servicing, but you might need to replace it altogether. A damaged or collapsed duct will need to be removed, replaced, and re-sealed if that’s what is causing the blockage of air in your system.

What Does It Typically Cost To Repair A Frozen Air Conditioning Unit?

In most cases, you can expect to pay between $200 and $3,500 to repair your frozen air conditioner, if it’s possible to fix. The average cost sits at around $800.

If dirty filters or blocked vents are the underlying problems, clearing them and restoring airflow will cost nothing more than a service call to your HVAC repair technician. They can also thaw the evaporator coil and inspect all of the components for damage, and the total will likely be around $200.

If a refrigerant leak is causing your problem, you might need to consider replacing your outdoor unit altogether. This is the most expensive fix for a frozen AC, and you will likely pay around $3,500-$4,000 for the replacement. If you opt for a refrigerant refill instead as a temporary fix, expect to pay between $250 and $500, depending on how much freon needs to be added.

If a damaged blower motor is your issue, replacing it usually costs around $600, but it can be as expensive as $900, depending on which motor is damaged.

A damaged fan can be as inexpensive as $200 to fix if the voltage is a problem, but a replacement will usually cost around $600. The longer your AC runs without the fans working correctly, the more likely your compressor is to fail. Replacing the compressor motor can bring your repair costs up to around $2,000.

Finally, a collapsed duct will usually be a straightforward repair. You can expect to pay around $200 for the labor and between $100 and $300 for materials in most cases.

How To Prevent Your Air Conditioner From Freezing Up

With many of the expenses to fix a frozen AC reaching into the thousands of dollars, most homeowners would benefit greatly from preventing the problem in the first place. Below, we’ll discuss three ways you can help prevent your system from freezing and requiring costly repair.

1. Replace Your Filters Regularly

One of the easiest and most affordable fixes is to check and replace your HVAC filters routinely. They should be swapped out every three months on average, but you might want to change them more regularly if you have pets whose hair can contribute to clogging. Replacing your filters is an easy DIY job that can potentially save you thousands of dollars in damage.

2. Inspect Your Vents and Ducts

Another easy way to avoid a frozen AC unit is to check your vents and ducts regularly. If at any point airflow is impeded, you’re at risk of freezing near the evaporator coils. A simple solution is to make sure your vents aren’t blocked by furniture and your ducts remain healthy and sealed throughout the year. A brief inspection when you change your filters every three months should be sufficient.

3. Schedule Routine Maintenance

Finally, one of the most comprehensive ways to prevent your AC from freezing is to remember to schedule routine HVAC maintenance. A certified technician will be able to inspect every component in your HVAC system for proper functionality, and they will repair or replace any pieces that are damaged or could fail in the near future. This preemptive service will give you peace of mind and could end up saving you thousands of dollars down the road.