AC Evaporator Coil Frozen? (Causes & How To Thaw It Out)

Frozen Window Type Air Conditioner

No appliance works harder and longer than air conditioners. They keep you and your loved ones cool for hours on end, especially during the scorching summer heat.

However, sometimes your AC unit may get extra ‘cool,’ causing it not to operate correctly. One such component that can freeze up is evaporator coils.

Evaporator coils are critical components in the heat-exchange process; there is no heating or cooling without them. Wondering what to do if the evaporator coil is frozen? Read on:

What Causes The AC Evaporator Coil To Freeze?

Here are a few reasons why your AC evaporator coils freeze over:

Dirty Air Filter (Lack Of Airflow)

One of the most common causes of frozen AC coils is a dirty air filter or lack of proper airflow from the blower. This can be due to several different reasons such as:

  • Improper or tight sized filter
  • Damaged or undersized ductwork
  • The dirty air handler or heat pump
  • The blower motor or fan isn’t operating properly
  • Blocked return vent

Dirty Evaporator Coils

If the evaporator coil attracts too much debris and dirt, it may obstruct the heat transfer process. In addition, dirty evaporator coils find it hard to absorb heat.

Therefore, it’s essential to clean your AC coils regularly. Call a professional if there’s too much dirt and dust in your AC coils.

Refrigerant Problems

Refrigerant is the chemical running through the coils, changing temperature and pressure to absorb the heat.

However, if it trickles, the inadequate pressure will force it to absorb additional heat than usual. This makes refrigerant coils freeze up.

Rather than adding more refrigerant by yourself, it’s better to let the professionals fix the issue or replace your coil altogether.

Outdoor Temperature Too Low

Your air handler and heat pump will not operate correctly if the outside temperature is less than 60 degrees.

Just like how the AC coil freezes up when there’s limited airflow or a dirty air filter, it can also frost up if the outdoor temperature is extremely low.

Frozen AC Evaporator Coil

Clogged Drain Pipe

When there’s excessive humidity, your AC coils work harder to remove too much moisture from the air. Once the moisture is taken out, condensation occurs and is drained from your house.

That’s fine unless you’ve got a jammed/clogged drainpipe that may lead to a frozen evaporator coil. This way, not only will you have a blocked drainpipe, but you will also have a frozen coil.

Malfunctioning Thermostat

Do you know that the thermostat works along with your air conditioning system by routinely monitoring its temperature and controlling how hard it needs to work to maintain a constant temperature?

If a faulty thermostat senses a wrong temperature or controls your AC unit improperly, it may cause the system to work harder and eventually wear out.

Also, if left unchecked, your overworked air conditioner may develop frosty AC coils.

Faulty Defrost Cycle

Air conditioners have a defrost cycle, which helps keep ice and frost from heaping on the AC coils. It works by reversing the refrigerant flow, thawing all the ice present on the outside.

However, if this cycle malfunctions, it can’t remove frost and ice from AC coils.

Signs & Symptoms Of Frozen AC Evaporator Coils

No matter how your AC coils frost up, the outcome is typically the same, i.e., your air conditioning system fails to cool your house effectively.

Unsure whether you’ve got a frozen AC coil? Here are a few key signs and symptoms of frozen AC evaporator coils:

AC Is Not Cooling

When AC evaporator coils freeze up, the first indication will be that you won’t achieve the desired room temperature.

If you’re sweaty despite the AC being on or notice high humidity levels, your AC unit might be malfunctioning!

If you think the coil is frozen, call your HVAC technician immediately rather than poking around in the system yourself – it can be pretty risky.

Visible Ice Around The Outdoor Refrigerant Line

Another common sign or symptom of a frosty evaporator coil is ice spreading to the outdoor refrigerant line. If this is the case, the issue is even more severe.

Air conditioning systems develop ice buildups when their refrigerants fall below 32°F, causing them to frost as they move through the coils.

The Coil Has Condensation And/Or Ice Formations

A coil that has been frozen for a long time can cause AC units to break down completely. This occurs when condensation builds on the coil, leading to freezing during operation.

This formation of ice on the evaporator coil blocks the heat exchange process with indoor air, preventing your system from providing cool air in any case.

Clogged Condensate Drain

If there’s a large quantity of stagnant water in the condensate drain, chances are it’s blocked or clogged.

In addition to that, if the condensation drain fills up too early, it’s probably that your air conditioning system’s draining is clogged.

Since a blocked condensate drain traps water in an AC unit, the coil will freeze eventually. Not just that, the humidity in the draining line can also frost, causing your unit to shut off.

Increased Energy Bills

If your monthly electricity bills have increased tremendously without any change in usage pattern or weather, it means your system is working harder than usual due to frozen evaporator coils.

Since frosty coils are less efficient and effective at eliminating heat from indoor air, your unit will work longer and harder.

Also, if you want to achieve your desired cooling, you may need to run it for extended periods.

Signs of Frozen AC Evaporator Coil

How To Thaw Frozen Evaporator Coil Of Your Air Conditioner

While most AC evaporator coil issues require an HVAC professional inspection, there are a few things that you can do to get things going.

Want to know how to thaw your frosty evaporator coils? Here’s your ultimate guide to thawing AC frozen coils:

Let The Coils Thaw

You should first switch off your air conditioning system and give frozen coils some time to defrost.

Do it by shutting off the system from your breaker. Then, leave it for a day at least so that coils thaw completely.

However, if you can’t wait for the entire day and want to speed up things a bit, you can use a hairdryer.

While using the hairdryer, you’ve to be extra cautious so that you don’t overheat AC evaporator coils or lines running through it.

For moderate freezing, there’s no need to turn off your unit. Instead, just let the system run on fan-only mode. It allows air to thaw the freezing without even shutting down the air conditioner.

Check The AC Unit’s Airflow

The next stage involves checking your AC unit for inadequate airflow. That’s because air filters often get clogged with debris or dust.

This prevents the air from a smooth flow, causing ice to build on the AC coil surfaces.

This is why it’s best to examine air filters of AC systems and have them replaced or cleaned to provide proper airflow.

In addition to that, ensure the AC coil is also free of debris and dust. Clean it straight away if you notice any debris, algae, or mold growing on the coils’ surface.

Check Malfunctioning Or Dirty Blowers

Inspect the air conditioner’s blower thoroughly for signs and symptoms of dirt or malfunctioning. Sometimes, a faulty or dirty fan can result in weak airflow, leading to coil freeze up.

If this is the case, you should call your professional HVAC technician to do a deep checkup and maintain the AC fan.

Check Levels Of Refrigerant

Low refrigerants create a low-pressure environment inside the coolant lines, making coils’ outer temperature fall under the freezing point. This allows the condensate to freeze over.

Typically, low refrigerants are caused due to a leak within the air conditioning system, mainly at the faulty valve or within the AC coil itself.

If it’s a refrigerant issue, let your HVAC professionals deal with it, as recharging and measuring coolant is quite a dangerous task to perform.

Check For Any Physical Damage

Lastly, check your AC evaporator coils for any symptoms of physical damage. Things such as dented pipes, damaged fittings, or bent fins can lead to freezing issues.

Call your professional in case of any damage and avoid using it until it’s fully repaired.

How To Prevent Evaporator Coils Frozen?

Preventing evaporator coils from freezing helps avoid expensive repairs and helps save money on utility bills, and offers the desired cooling.

Here’s how you can prevent evaporator coils from freezing:

  • Make sure to clean or replace filters every three months to maintain proper airflow through the coil. However, if you’ve got pets or dwell in a relatively dusty location, maintain them every two months.
  • Keep your AC blower and motor maintained so that they blow adequate air throughout the coil.
  • Check your AC unit’s controls and thermostat so that it functions within its set temperature range.
  • Don’t forget to recharge your coolant or refrigerant if its levels are extremely low. Make sure to routinely check refrigerant pressure and call your professional from time to time for its maintenance.
  • Keep your AC evaporator coils clean to provide adequate heat exchange from indoor air to coolant flowing through coils. This way, the unit operates at the highest efficiency, reducing the dangers of frozen coils and higher utility bills.

If you’ve got a frosty evaporator coil and somehow manage to thaw it, the issue will occur unless you solve the primary cause. However, if you keep your AC system maintained, there’s a very slim chance it will happen again!

People Also Ask (FAQ)

How long does it take for an ice in an evaporator coil to thaw?

Typically, it may take an entire day for ice to thaw, but it can be longer than 24-hours if the system is wrapped in solid blocks of ice. However, with the unit off, the ice will eventually melt.

Can I pour water on frozen AC?

Yes, you can! If you intend to melt the ice faster, you can pour warm water on your frozen evaporator coils. Also, the water doesn’t have to be hot; running tap water can also do the task.

How do you defrost the frozen coil fast?

Here’s how you can defrost the frozen coil fast:

  • First thing first, turn your thermostat from ‘cool’ to ‘off’ setting
  • Then, turn on the ‘blower fan.’ It provides nonstop air to your AC system’s frozen evaporator coils
  • Lastly, if necessary, replace your air filter

Can I turn on heat to defrost AC?

Yes! You can defrost AC using a hairdryer. First, make sure it’s on the lowest setting. Next, hold your hairdryer about 12-inch away from the evaporator coil. This is because excessive heat can damage your AC coils.


Frozen AC evaporator coils are a common problem that many homeowners face during summers. If you don’t act timely, it may affect your utility bills or cost you significantly. If you’ve got a frozen coil, thaw it with the help of this guide.

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Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.