What to Do When Your AC Unit Freezes Up

A frozen air conditioning unit can dramatically reduce efficiency, which can cause the AC to work much harder to cool your home. You may notice this if the unit is running a lot, but not cooling well. A frozen AC can also cause the system to not work at all. ACs can freeze even during the hottest summer months.

So, how does this happen, and what can you do when your AC unit is freezing up?


How Does an Air Conditioning System Work?

Air conditioners come in a variety of shapes and sizes, but they all operate on the same basic premise. An air conditioner provides cold air inside your home or enclosed space by actually removing heat and humidity from the indoor air. It returns the cooled air to the indoor space and transfers the unwanted heat and humidity outside.

A standard air conditioner or cooling system uses a specialized chemical called refrigerant, and has three main mechanical components: a compressor, a condenser coil and an evaporator coil. These components work together to quickly convert the refrigerant from gas to liquid and back again. The compressor raises the pressure and temperature of the refrigerant gas and sends it to the condenser coil where it is converted to a liquid. Then the refrigerant travels back indoors and enters the evaporator coil.

Here the liquid refrigerant evaporates and cools the indoor coil. A fan blows indoor air across the cold evaporator coil where the heat inside the home is absorbed into the refrigerant. The cooled air is then circulated throughout the home while the heated evaporated gas is sent back outside to the compressor. The heat is then released into the outdoor air as the refrigerant returns to a liquid state. This cycle continues until your home has reached the desired temperature.


Signs Of a Frozen Air Conditioning System

  • Minimal Cold Air Coming Out Of the Vents

The most obvious sign is a lack of air coming out of your vents and the temperature in your home rises. The ice in the coil has restricted the airflow causing the supply air to basically trickle out of the vents.

  • Frost On the Refrigerant Lines

The most obvious visual sign is frost on the copper lines. The frost builds up and shows on the copper coming out of the system. In severe cases, a full block of ice can form which can take a while to thaw out.


What Causes an AC Unit to Freeze?

Air conditioners freeze when something disrupts the functioning of the evaporator coil, causing the refrigerant to cool too much, fall below freezing, and ice over.

There are some things that can lead to an AC freeze-up:


  • Low Refrigerant Levels

If you find yourself asking why my air conditioner freezes up in the summer, low refrigerant levels may be to blame. An AC unit needs a certain amount of refrigerant to ensure proper cooling performance. When the refrigerant levels fall below the needed amount, the balance within the system is affected and can cause your air conditioner to freeze. Frozen coils are one sign that your AC may have low levels of refrigerant and should be addressed as soon as possible. The only way to properly fix this issue is to contact professional technicians who can evaluate and restore your cooling system’s refrigerant.


  • Dirty Air Filters or Blocked Vents

Air conditioning units can suffer from freezing due to a buildup of dirt or blockage in the air filters and vents. The most common cause of AC unit freezing is a dirty air filter or blocked vent. Air filters are designed to accumulate dust from the environment then blown into the system. Pet dander, lint and other particles can line vents if not cleaned and vacuumed regularly. Without proper airflow into the system, it quickly becomes overloaded, leading to the unit freezing. Taking preventative measures such as regularly changing air filters, cleaning vents regularly and making sure there is not any blockage around them should help alleviate any issues with frozen air conditioning units.


  • Damaged or Faulty Wiring

It is important to check all wiring from the thermostat, furnace, and the outside condenser unit in order to prevent an unexpected freezing. If any electrical wiring appears burnt or torn, it should be inspected and transformed by a professional due to safety concerns. Doing routine maintenance for your AC unit regularly throughout each year can help you catch these small problems before they snowball into costly repairs.


  • Clogged Condensate Drain Line

As your air conditioner chills your residence, it removes humidity from the interior, making it more comfortable. However, sometimes dirt, mold, and other substances form inside your unit’s condensate drain line, preventing it from disposing of excess water. This forces the water into the secondary drain pan to prevent the water from flooding your ceiling or floor.

However, the secondary drain pan can only handle so much water. Once the pan reaches a certain level, a safety switch turns on to prevent it from overflowing. The switch often restricts energy to the unit, causing the thermostat or condensing unit to shut off. Doing this each year will help keep proper airflow within your air conditioning system and prevent anything like frozen coils from happening in the future.


What to Do if Your AC Freezes Up

To avoid further damage, the first thing to do when your AC freezes up is to turn the air conditioner off. From the thermostat panel, switch the AC from “cooling” or “auto” to fan mode. Setting your AC in fan mode will help the system receive warm air to help the frozen AC line or coil defrost.


1. Thaw the Air Conditioner

Upon seeing the frozen parts of the air conditioner, you should immediately turn the unit off to prevent the problem the situation from deteriorating any further. Cutting off the power to the cooling system will stop the flow of cold refrigerant into the frozen area. The ice will melt by itself thanks to the heat of the surrounding air. However, the process may require hours to finish.


2. Dry the Air Conditioning Coils

Remember that melting the ice is just the first part of the process towards normality. The second is dealing with the inevitable wetness across the AC. This can get messy. Dry things up before using the air conditioner. Use an external fan to hasten drying or run the blowers to achieve the same goal. This may take an additional hour or so. Leave it for a while and come back for inspection. If the inside has dried up, then you can resume normal operation.


How to Prevent Your AC from Freezing

There are a lot of reasons why the coils can freeze. The easiest way to prevent a frozen air conditioner is to continuously inspect and replace your air filter. A dirty filter reduces airflow and causes the refrigerant cycle to lose the balance of air and line pressures. The biggest cause is normally a failure in the refrigerant line. The vast majority of the time compromised refrigerant lines cannot be repaired and a new system component is then needed to be replaced.


1. Install a Humidistat

If you live in a high-humidity area, like along the southeastern coast, the amount of condensation may be too much for your system to handle. A humidistat can keep your indoor moisture levels under control, which could be beneficial to keep mold and mildew problems from rearing up, as well as reducing the chances of your AC freezing.


2. Inspect/Replace the Air Filters

Make it a habit to regularly inspect your AC filters. Clean or replace them as suggested by the manufacturer, which is usually every 60 to 90 days. However, if you’re in a high-pollen area, check the filters more often. Clogged filters impede airflow which could cause AC freezing issues.


3. Schedule an Annual Maintenance Visit

You may be asking yourself how often you should service your air conditioner. If you are wondering, then it is probably time! Before summer really comes into full swing and you are melting in the scorching heat, make sure you get your AC serviced by a local Aire-Tech professional.

A tune-up is a preventative AC maintenance service that prepares your air conditioner for increased use in warmer months. Think of it as an annual physical for your air conditioner, ensuring key components are running well. During an AC tune-up, a professional comes to your house to inspect your indoor and outdoor AC components. The visit is short and relatively inexpensive.


4. Add a Smart Thermostat

A programmable thermostat is much easier to manage because a conventional one requires you to readjust it daily manually. But if you do not want to do that, a smart thermostat is all you need. It is even better if it has a Wi-Fi feature, so you can even control your home temperature if you are away from home.

Maintain Your HVAC System

Change the air filters in your heating and cooling system every few months. If you have pets, or an unusually dusty house, you may need to do this more often. Many homeowners opt for a cheap filter, but higher quality filters can make a big difference in both air quality and the efficiency of your HVAC system.

You should also periodically clean your air ducts and vents. If you have a lot of dust in your heating and cooling system, it can find its way into your living space. Vacuum visible dust from vents and consider a professional duct cleaning if you’ve never had it done.

  • Changing your furnace filter regularly
  • Clean ducts regularly
  • Schedule semi-annual maintenance for your HVAC system
  • Whole-house air purifiers remove dust and pollutants
  • Consider an Air Purifier


Give Us a Call

One of your worst fears is having to replace the heater or air conditioner in your home. But with due diligence, you can prevent a premature replacement and the associated costs.

If your system needs repair or inspection, call Aire-Tech on 951-926-1002. You can also visit our Contact page and complete the contact form.