How to Unfreeze an AC Unit?

It might come as a surprise to some that air conditioners that we tend to use only when it’s hot outside can actually freeze up. What should you do, in such a situation?

To unfreeze your AC unit, you should turn the thermostat to ‘off’, switch the fan to ‘on’, and change the dirty air filter. It can take the air conditioner up to 24 hours to defrost; during this time keep an eye on the drain pan and the condensate drain line.

How Do You Unfreeze an Air Conditioner Fast?

There is a way to quickly unfreeze an AC unit, but do bear in mind that it won’t fix the root cause of the problem. The air conditioner is freezing up for a reason and the sooner you find out what’s actually going on – the better.

How to unfreeze AC unit? Follow these simple steps.

Read: Where Is The Heat Pump Located?

Turn your thermostat to ‘off’

If you see ice on your AC, it means that the system is sending too much of the cold refrigerant to the outdoor unit. Normally, the latter should be receiving the refrigerant in the form of hot gas.

By turning your thermostat off, you are stopping the system from sending even more refrigerant to the outdoor unit. If you don’t do that, the compressor can get damaged.

Turn the fan setting to ‘on’

By turning on the fan, you are forcing the AC to start blowing warm air over the frozen coils. In a nutshell, the blower motor will be pulling in the hot air from your house and then pushing it over the refrigerant coils.

This will make the ice on the unit thaw.

  • Change the air filter, if necessary
  • Turn the AC back on

As soon as all the ice has thawed, you can switch the unit on. During the next few days, make sure to regularly check the air conditioner’s ‘well-being’.  

There are two main things that you should keep an eye on, while the ice is melting.

The drain pan

During this process, more water is going to enter the system. Bear in mind that the melting ice can end up overflowing the drain pan.

All you can do is put some towels around the indoor unit. The chances are high that there will be water leaks.

The condensate drain line

The water from the thawing ice drips in the drain pan and then goes through the condensate drain line. However, the ice can pick up quite a lot of dirt along the way and clog the line.

In such a case, the water is going to come back to the drain pan and overflow it.

If everything was okay and then you started noticing water leaks, then make sure to check the drain line and get rid of the clog, if there is such a need.

If the instructions above did not help and your outdoor unit started to ice up again, then you would have to call a professional to deal with the problem. 

Read: Why Does Heat Pump Make A Loud Noise When It Shuts Off?

How Long Does It Take to Thaw a Frozen Air Conditioner?

It might take anywhere between 1 and 24 hours to defrost your outdoor unit.

The timeframe depends on a few factors:

  • The extent of ice buildup (the sooner you have spotted the problem, the better)
  • The size of your unit (the smaller the unit, the less time it’s going to take)
  • The outside temperature (on a rainy, snowy, or cool day, it will take your unit a lot longer to defrost)

Read: Where Is The Reset Button On A Heat Pump?

What Causes an AC Unit to Freeze Up?

Lack of airflow

The most common reason for a frozen unit is a dirty filter. If the filter is clogged, the blower won’t have enough air to push over the coils.

A collapsed or blocked air duct might also be to blame. As well as blocked or closed return and supply vents (don’t place furniture or curtains in front of them).

A low level of refrigerant

If there is not enough refrigerant in the system, it usually indicates that there is a leak.

As a result, the unit won’t be able to maintain the right pressure needed for proper operation. If the pressure is not high enough, the refrigerant can’t get hot.

Mechanical problems

A blower motor is a component that makes the fan push air through the system. If the motor had gone bad, then there won’t be enough air circulating in the unit.

Hint: when a blower motor is failing, you will usually hear rattling sounds coming from the air conditioner.

Clogged condensate lines

If the drainage line is blocked, then water can easily get trapped right next to the evaporator coil, and it won’t take too long for the H2O to freeze.

A power issue

If the blower motor and, consequently, the fan are not receiving enough power, they won’t be able to operate as effectively (push the air through the system), and the coils are going to freeze.

A dirty coil

If there is dirt or dust buildup on the coil, the air won’t be able to warm up the element. So, the coil will freeze.

It is normal for air to carry some dust and your coils do require regular cleaning, so annual professional check-ups are incredibly important.

Low outside temperatures

Finally, your unit might have frozen up simply because it was abnormally cold outside (this can happen not only in the winter but also in the summer).

Different air conditioners are designed to have different optimal temperature settings. When the temperature gets lower than the one the AC is ‘used to’, the unit might freeze up.

A programmable thermostat can take care of a problem. The device is simply going to shut the AC down whenever the temperature gets below 60 F, for example.

Read: Why Air Conditioner Heat Mode Not Working?

Will Frozen AC Fix Itself?

Well, if you switch the air conditioner off and the outside temperature gets warmer, then the unit might end up defrosting.

But it is definitely not recommended to follow such a scheme.

In such a case, you are not going to get rid of the root cause and the AC will freeze up again sooner or later. Moreover, by leaving the unit all to itself, you won’t be able to keep an eye on the drain pan and condensate drain line which can lead to serious damage.

So, as soon as you have noticed that your AC is frozen, you should start taking certain steps to help it.

Read: What Is The Best Way To Heat A Large Space?

Is a Frozen AC Unit Dangerous?

Keeping the air conditioner running while it’s frozen is a bad idea.

First of all, you are going to waste a lot of energy and money as a frozen unit is not able to operate efficiently.

Secondly, your compressor can fail. Fixing or replacing this part is a time- and money-consuming process. Moreover, other components might have also gotten damaged while the system was operating.

Can You Pour Hot Water on a Frozen AC Unit?

In general, it is considered safe to use hot water to thaw the ice on your outdoor unit.

The water doesn’t have to be extremely hot, even warm H2O will do.

However, remember that even though such an option will help you defrost the unit a bit faster, it won’t eliminate the root cause of the problem. You would still have to check the filters, the refrigerant level, and so on.

Read: Cost Of The Heat Pump: Everything You Need To Know About It

Can a Dirty Filter Cause AC to Freeze?

Yes, the air filter is the first that you need to check when your unit freezes up.

Regularly changing the filter is a great way to keep your air conditioner from forming ice on the outdoor unit. Moreover, it is a relatively easy and cheap fix that you can perform on your own.

A dirty filter can lead to a wide range of other problems as it makes the system work a lot harder than necessary.