Three Reasons Why Your AC Unit Freezes Up & What To Do

If you’re frustrated with your AC unit freezing up either in the cold winter or even warm summer, there might be a couple of different reasons causing it.  Even if you have tried to clean it multiple times, that might not be the only thing you need to do to prevent a freezing problem. Whether your AC’s internal unit is covered in ice, has frozen HVAC coils, refrigerant lines are covered in frost, or you barely get any air from the vents even if the air conditioner is on at its highest cooling setting, this article can help you figure out why your ac freezes.

How do Air Conditioners work?

At the very basics, an air conditioner collects the warm air in a home and starts a process that produces cold air by removing the heat from it.

When the AC’s air feels cold, it means that the molecules in the air aren’t compressed and are moving slowly due to low energy levels in them. Hence, the temperature of the air falls and cools. When the opposite happens, the air feels hot. 

Essentially, an indoor coil remove the heat from the inside air and then uses the refrigerant to pass it to the outdoor unit coil to release it outdoors. An air conditioner expands the refrigerant in the evaporator coil, which is a chemical that causes a cooling effect. When the refrigerant in the coil cools down, the AC provides cool air and actively eliminates the warm air from a home.

However, if something inside the unit isn’t functioning properly, the refrigerant coil cools down drastically, and this can cause the AC to freeze up. In other cases, it can cause your AC to stop producing cool air.

Why An AC Freezes

ac unit freezing

Here are some of the most common causes of why an air conditioner freezes.

Restricted or Blocked Air Flow

Airflow refers to the air that is flowing over the evaporator coil. Generally, the AC sucks in the indoor air and transfers it to the evaporator coil, which uses the refrigerant to cool it down before releasing it back into the room. If there is anything blocking this normal flow of air, this will cause it to work insufficiently. 

One of the common reasons for blocked airflow is dirty air filters. Just as you would for air filters in air scrubbers, check on them regularly and wash air filters with water and vinegar every few months. Air filters are available at low prices, so if you don’t want to waste time cleaning a dirty air filter and get the most efficiency, just buy air filters in bulk and switch them out when needed. 

Other causes for your ac freezing can be closed supply vents, dirty evaporator coil, return grills covered by curtains, drapes, damaged blower fan, and inferior ductwork.

Low levels of Refrigerant Or Refrigerant Leak

When the refrigerant levels are running low or a refrigerant leak occurs, the pressure drops down, and the temperature decreases. This can cause the evaporator coil to cool down much more than it should. There HVAC gauges that can read the refrigerant levels in an HVAC system, to see if this is the problem.

The best way to deal with this issue is by calling an HVAC professional unless you’re experienced or even qualified to use a refrigerant leak detector to find the leakage point. There are two options that most experts will give you if this is the problem. First, check the repair estimate. If the repair is minor, refill the AC. If the repair is expensive, look for another air conditioning system and replace your current unit.

Drainage Problems

When the weather is hot, warm air passes over the evaporator coil. The evaporator removes heat and moisture from the air. This can cause the water vapors to condense within the AC. 

Typically, the water slowly drips down into a pan, and then it travels out via the floor drain. However, if something is blocking the drain, the water quantity increases, and it starts to freeze. In these circumstances, it also freezes up. 

To prevent this from happening, keep checking the drainpipe at least once a week. If the water is dripping from the floor drain, the AC works perfectly. However, if it’s not, you need to check the evaporator and see if it’s covered in ice.

frozen ac pipe

How To Fix A Frozen AC Unit

As soon as you notice that you have a frozen HVAC system, turn the air conditioner off immediately. Switch it off from the main power supply as well. Running your unit like this will not only waste your money but can also damage the compressor, which is a pretty expensive component.

Here are some of the ways you can fix and prevent the air conditioner problem:

  1. Check the air filters. If they are dirty, wash them. If they are damaged, replace them.
  2. Wait for the ice to melt. For this, you need to check the condensate drain and ensure that it’s not blocked. To speed up the melting process, you can also use a blow dryer and use it on the AC evaporator.
  3. If you’re an expert and know all the components of the AC well and other air conditioning features, you can try opening up the ductwork and use a wet-dry vacuum to suck out all the water. But unless you’re licensed or have the right HVAC equipment, consider calling an HVAC technician who will have the right software, knowledge and all sorts of tools like pumps to fix your air conditioning system.
  4. Constantly check the following components and do regular maintenance on them: 
  • Refrigerant level
  • Air filters
  • Supply Vents
  • Condensate drain
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Justin Edwards

Justin Edwards is an HVAC contractor in Ann Arbor, Michigan. Before working in HVAC, he worked in all sorts of other contracted-related jobs. When he's not doing HVAC-related work, he's writing DIY articles and sharing his expert insights.