March 1, 2024
Reasons Your AC is Freezing Up and What to Do

Are you experiencing issues with your air conditioning system frequently freezing up? A frozen AC can be a serious issue since it has the potential to cause extreme damage, so it’s not a problem you should ever ignore. Luckily, there are only a handful of issues that can cause an AC to start freezing up, and some of them are things you can overcome yourself.

What to Do If You Suspect Your AC Is Frozen

A frozen AC system is an easy issue to spot. When the evaporator coil freezes and gets coated with ice, the system will no longer be able to remove heat from your home. This means that the temperature in your house will quickly start increasing. The air coming out of your vents will also be hot since all the system can do is circulate hot air when it is frozen.

If your AC does freeze up, you should always shut it off immediately. Allowing the system to continue running when frozen puts the compressor motor in the outdoor condenser unit at high risk of seizing or burning out.

When an AC functions normally, the refrigerant captures enough heat that it naturally changes from a liquid into a gas as it moves through the evaporator coil and gets pumped back outside. When the system freezes up, it leads to the refrigerant remaining in a liquid state. If liquid refrigerant enters the compressor, it can quickly boil and cause some of the oil that lubricates the compressor motor to burn off. This can then lead to the motor not being properly lubricated, which can cause it to burn out.

A burnt-out compressor motor is an extremely expensive issue to repair and can potentially cost about as much as installing a whole new condenser unit. That’s why it’s important that you shut the system off immediately if it freezes to prevent damaging it. Depending on what caused the system to freeze, it may be something you can quickly fix on your own. All of the following issues are really the only things that can cause an AC to freeze, so it is worth checking a few things before calling in the help of an AC technician.

Clogged Air Filter

A clogged air filter is by far the most common issue that will lead to an air conditioning system freezing up so it is always the first thing to check for. The issue is that a clogged filter greatly restricts how much warm air can be drawn into the system. The refrigerant in the system is extremely cold when it first enters the evaporator coil and then quickly starts warming up as it captures heat from the air. The problem is that a dirty, clogged air filter will massively reduce the amount of warm air coming into the system and moving across the evaporator coil. If there isn’t enough warm air continually flowing across the coil, the refrigerant will stay cold enough that all of the condensation on the coil starts freezing.

AC manufacturers generally recommend replacing the air filter in your system every three months. However, there are often times when the filter will start clogging up more quickly and need to be replaced sooner. This is why we recommend taking out the filter and inspecting its condition every month. As soon as the filter starts getting darker colored, it is time to replace it.

If your AC freezes up and the filter is quite dirty, replacing it will often solve the problem and prevent it from freezing up again. However, you need to wait at least an hour or two to make sure that the evaporator coil completely thaws before trying to turn the system on again. If the system does end up freezing again after replacing the filter, you’ll want to leave it shut off until you can have a technician inspect it.

Closed or Obstructed Vents

The other thing you should check if your AC freezes up is that all of the supply and return air vents are fully open and not clogged with debris or blocked by furniture or other items. The return vents are where warm air is drawn into the system. Although these vents generally can’t be closed, they will prevent enough warm air from coming into the system if they are clogged or obstructed.

The supply vents are where all of the cool air from the system flows out. To work properly, the majority of the supply vents in a home need to be fully open. Having one or two closed vents typically isn’t a problem, but any more than that can lead to the system freezing up. The issue is that when too many supply vents are closed or obstructed, lots of air gets trapped inside the ducts, which leads to the pressure increasing. When working properly, an AC system is constantly drawing in and blowing out the same volume of air. When the air starts to back up in the supply ducts and the pressure increases, it makes it much more difficult for the blower to bring sufficient air back in and can lead to the evaporator coil freezing.

Dirty Evaporator Coil

A dirty evaporator coil is another common culprit that can cause an AC to freeze up. Some dust and dirt always end up collecting on the evaporator coil over time, which is why the coil always needs to be cleaned every year as part of a preventative AC maintenance service. If the coil isn’t cleaned regularly, so much dust can build up that it effectively insulates or shields the coil. This means that the warm air coming into the system can’t come into direct contact with the coil, which greatly reduces how much heat the refrigerant can absorb. Again, if the refrigerant isn’t capturing sufficient heat, it may stay cold enough that condensation on the coil begins freezing.

This is an issue that you will need to have a technician check for and fix. Trying to clean the coil yourself is always a bad idea since you could easily damage it and cause a refrigerant leak or make the system far less effective.

Dirty or Malfunctioning Blower

The blower or fan also needs to be cleaned regularly since it also collects lots of dust. When the blower gets too dirty, it can make it impossible for it to circulate sufficient air to prevent the system from freezing up. The same issue can also occur if the blower is malfunctioning or starting to wear out. In this situation, a technician will always fully clean the blower and then test it to see if it needs to be repaired or possibly replaced.

Low Refrigerant Charge

Your AC system needs to have the correct refrigerant charge or level to work properly. When the refrigerant charge is low, it leads to the pressure in the system decreasing. As the pressure decreases, the temperature of the refrigerant also decreases. If the charge is too low and the pressure is below a certain point, the refrigerant can get so cold that the evaporator coil constantly freezes up.

The refrigerant in an AC system flows in a closed loop, which means that the charge should always stay the same. If the charge is low, it often indicates that there is a leak somewhere in the system. However, low refrigerant charge can also occur due to improper maintenance or installation.

Beltway Air Conditioning & Heating is a locally owned company that provides professional HVAC services to residential and commercial customers in Hanover and the surrounding areas. Our technicians specialize in air conditioning maintenance and repairs and can help you overcome any issues causing your AC to freeze up. We also specialize in AC installation and the full range of heating services, so contact us today for any of your home comfort needs.

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