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Why Is My Air Conditioner Freezing Up?

Updated: Dec 12, 2022

From providing a cold temperature in the hotter months to staying ambient in milder seasons, many people rely on their AC every day to maintain a better standard of living. So when your unit freezes, and you're left with no air conditioning, it can ruin your whole day.

Read on for our advice on air conditioning maintenance and how to unfreeze a window ac unit.

Why would an AC Unit freeze up?

The first thing to understand when uncovering why your AC unit is freezing up is how exactly a standard unit is made.

Many air conditioners come with a cold coil inside, which requires consistent airflow to provide air of the correct temperature.

This airflow from the room is a higher temperature than the fresh air the machine emits, and this constant cycle is what produces air of the correct temperature for the space you're cooling.

As part of this process, water vapor the unit pulls from the room is condensed and then drained off.

Because of this coil, and the requirement for airflow, an AC unit can become frozen by the airflow being removed from the process, leading to the condensed water within the unit freezing around the coil, instead of draining away.

This lack of airflow could be caused by a blockage or even a dirty or malfunctioning air filter on an AC.

A closed air register may also contribute to this lack of airflow.

The other common cause of a frozen AC unit is a faulty temperature gauge or thermostat within the machine, causing the condensed water to freeze around the coil.

If ice blocks the drainage area, the freezing will continue or become worse over time as condensed water continues to be trapped and freeze.

Other blockages can also cause this problem, with anything from household debris to twigs or leaves causing blockages.

An AC Unit freezing isn't just a problem when it comes to cooling a room - it can actually cause harm to the air conditioner, and also can increase the cost of running the unit as it is not able to cool the room efficiently.

How do I prevent my AC unit from freezing up?

Prevention of your AC unit freezing is relatively simple, and all it needs is consistent care and attention on a regular schedule. This can be performed through small checks of the machine on a weekly basis, so any issues are caught early and before they cause a severe problem or breakdown.

The following checks should be taken weekly or monthly to prevent your AC unit from freezing:

  • Checking the drainage system for blockages

  • Checking and replacing the filter as and when needed

  • Ensuring vents or air registers are open and not blocked

  • Check the fan and speed of the fan

  • Listen for any unusual or unexpected noises

  • Check the level of refrigerant

  • Ensure the thermostat on the AC unit is set to the right temperature

For any of the above you feel you cannot do, choosing to use a maintenance company to check on your AC unit every few months may be a good alternative, ensuring that your AC unit is cared for and will remain working for longer.

It may also be the case that to prevent future freezing of your AC you need to upgrade to a new, more efficient model that has less chance of freezing.

Keeping the air conditioning maintenance on your unit up to date can prevent any number of problems with your unit before they occur, saving you both time and money.

Why is my AC line frozen?

The AC line, or refrigerant line on an air conditioning unit, is what provides your unit's cooling coil, or evaporator coil, with the 'cold' it needs to cool rooms. But when problems occur with the coil itself, this can result in the outside of the AC line becoming covered in ice and often completely frozen.

This line can become frozen when the refrigerant inside the line becomes too cold, resulting in the AC unit not working as it should, and the frost effect on the unit itself.

This can be as a result of a blockage to drainage, leading to the condensed water freezing the coil itself, and the line freezing following this.

However, there are also other causes of an AC line freezing than a simple blockage. A coil that is not functioning correctly or that is, itself, dirty will result in less efficiency of the unit and colder atmosphere inside the coil, resulting in the coil and line freezing.

A reduced amount of refrigerant in the line may also cause this appearance and can result from refrigerant leaking from the line itself.

How do I unfreeze a frozen ac unit?

Depending on how severe the freeze is, and the cause of the freeze, there are some DIY options available for the care and management of a frozen AC unit.

The following steps can be taken to unfreeze an air conditioning unit from home:

  • Unplug the air conditioner from any electricity source

  • Check and clean all filters before retrying the unit to see if the problem is resolved

  • Check and open any closed airflow areas, and then retry the unit

For the removal of ice and frost quickly, it has been suggested that a warm air source, such as a hairdryer, can be used on a unit that is not connected to electrics to melt the build-up faster.

However, this method should be performed carefully, to ensure that water doesn't access any electrics or cause other harm. It should be checked that there are no blockages in the drainage system before attempting this.

If the above steps allow the unit to function properly, you have resolved the problem. However, if these steps do not work, you may need to hire a professional in order to care for your air conditioning unit correctly and defrost it in the appropriate way.

For those that have window AC units - here is a great video that shows you how to unfreeze the unit.

How long does it take a frozen AC to defrost?

The length of time it takes to defrost an AC unit depends entirely on many factors, including the environment of the room the AC unit is in and the cause of the freezing itself.

In hotter temperatures, if blockages or airflow is resolved and has shown to be the issue, an AC unit can defrost in a short amount of time when left unplugged from electrics, and then used with the fan on.

Choosing to employ professionals for the management and defrosting of an AC unit can give you a more definite amount of time before you can use your AC unit again.

A plumber or maintenance worker will be able to advise you on the problem with your system, and how long it will take the unit to defrost based on their expertise.

If you're having trouble with a freezing AC unit, you're looking for air conditioning maintenance for your property, or you're simply concerned about the possibility of your AC units freezing, Deluxe Plumbing and Heating can help. Contact us today to find out more about our air conditioning repair services.


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