What Causes AC Coils to Freeze?

Frozen AC coils can severely impact the efficiency of your cooling system. In fact, frozen coils are one of the most common reasons AC units break down. Some signs that your AC coils are frozen include:



• Your AC unit does not blow cold air
• Your AC unit makes strange noises
• Your AC unit cools unevenly

The first step to rectify and prevent frozen AC coils is to understand the possible causes of this problem.

Low Refrigerant Level

The refrigerant is a chemical that absorbs heat from your indoor air and releases the heat outside. If your AC has a refrigerant leak, the refrigerant level goes down, and so does the pressure inside the evaporator coils. Consequently, the refrigerant may absorb too much heat. Each of these problems causes the refrigerant lines and the coils to freeze.

Furthermore, a refrigerant leak compromises the efficiency of your AC, which causes moisture from the air to accumulate and freeze on the coils.

You can quickly rectify this problem by charging the refrigerant, but this solution is only temporary. Therefore, you should let a professional inspect the entire system and address the root cause of the refrigerant leak to prevent the issue from reoccurring.

Dirty Air Filter

AC filters trap dirt, dust, pollen, and other airborne particles before they can enter your AC unit. Over time, these particles may accumulate and clog the filter, which reduces air circulation and puts strain on the AC unit.

Lack of adequate airflow puts the coils at risk of moisture accumulation. Moreover, since air has no passage, cold air will be trapped inside the air conditioning system. The cold air will eventually freeze the coils. Besides frozen coils, other signs that your AC filter is dirty include higher energy bills, bad indoor air quality, and frequent breakdowns

Experts recommend that you clean your AC filter and change the filter every one to two months. If nothing changes after filter replacement, have a professional inspect the entire system.

Thermostat Issues

If your AC's thermostat is faulty, the component will give false readings. As a result, your AC unit will either work overtime to achieve the desired temperature or shut off prematurely. Either way, thermostat issues put a lot of strain on the system and may cause the coils to freeze.

One easily noticeable sign of a faulty thermostat is significant temperature swings indoors. If the temperature fluctuates more than a few degrees, something is wrong with your thermostat.

You may also identify a faulty thermostat if your AC unit turns on and off frequently. The short cycling puts a lot of strain on the system and will eventually cause component failure.

If you suspect your thermostat is not working correctly, contact a professional to inspect the component. The HVAC expert can determine if the thermostat is the cause of the frozen coils and whether your AC has other underlying issues.

Clogged Evaporator Coils

The evaporator coils absorb heat from the indoor air. The coils consist of a series of metal fins that are very delicate and easily bent. Over time, these fins can become clogged with dirt, dust, and other debris.

When the coils are dirty, they cannot properly absorb heat. As a result, the refrigerant inside the coils may get too cold and eventually freeze.

You can clean the coils yourself with a brush or coil cleaning solution. However, if the coils are too damaged, you will need professionals to replace them.

Frozen AC coils put the entire system at risk and can lead to a complete AC breakdown. Contact us at Northwest Heating & Air Conditioning Inc. as soon as you suspect that your coils may be frozen. Our certified professionals will inspect your AC unit and repair or replace any damaged components.