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Why Is My AC Freezing Up?

It’s a hot day but your AC is freezing up and won’t turn on. Why is this happening?

The main reason your AC is frozen is because the evaporator coils (inside your AC unit) got so cold that they froze.

There are a variety of reasons your evaporator coils can freeze, including:

  • A dirty air filter
  • Blocked vents
  • Dirty evaporator coils
  • A refrigerant leak

Below, we'll look at each of these issues in more detail and how they can cause your evaporator coils to freeze.

Want to fix your frozen AC ASAP?

Contact Advantage Air Mechanical. We offer same-day AC repairs for your convenience.

Reason #1: Dirty air filter

If your AC is freezing up, your air filter may be dirty.

When your air filter is dirty, the amount of dust and debris in the filter can prevent your AC from sucking in enough warm air.

When not enough warm air is blown over the evaporator coils, they freeze.


Well, evaporator coils have a cold chemical agent, called refrigerant, running through them. When warm air is blown over the evaporator coils, this refrigerant absorbs the heat from your home’s air, which is how your AC cools your home. But, if your AC filter is blocked, and not enough warm air is passing over the coil, the coils can get so cold that they freeze. To prevent this, you'll want to regularly replace your air filter.

Clean (left) v.s. Dirty (right) air filter

Reason #2: Blocked vents

If your return vent is obstructed, your AC can only pull in a limited amount of warm air. Much like a dirty air filter, the lack of warm air blowing over the evaporator coils will cause the coils to freeze.

You’ll want to ensure all the return vents in your home are open so your AC can suck in the right amount of warm air.

Reason #3: Dirty evaporator coils

Another reason your AC could be frozen is that the evaporator coils are dirty.

While the evaporator coils are within the inside unit, the dust and dirt in the air can still find their way to the coils. If the layer of dirt is thick enough, it can prevent the refrigerant in the coils from absorbing enough heat from the air. If the refrigerant can’t absorb enough heat from the air, it will get super cold and freeze the coils.

If you think your evaporator coils may be dirty, you will need to contact an HVAC professional. The coils are hard to access and would require dismantling your AC, so it’s best to have a trained technician do the cleaning.

Reason #4: Refrigerant leak

Refrigerant is a cold chemical agent circulating throughout your AC system. It moves warm air from inside your home outside, cooling your home.

When there is a refrigerant leak and your refrigerant levels decrease, the pressure in your AC drops. With low pressure comes refrigerant expansion and colder refrigerant temperatures.

When the refrigerant gets too cold, the heat being transferred through the evaporator coil to the refrigerant also decreases so the coils end up freezing over.

Since refrigerant is a toxic substance, you need to contact an HVAC technician to repair the leak and refill the refrigerant.

Looking for an immediate fix for your frozen AC? Contact Advantage Air Mechanical

We pride ourselves on making the AC repair process as smooth as possible. This is why we offer easy 2-hour scheduling appointments and same-day repairs.

On top of convenience, we don't pay our techs on commission so you know we won't upsell you on unnecessary repairs.