Why Does My AC Keep Freezing Up?

Your air conditioning unit may do nothing for half of the year. But, as soon as the weather warms up you’ll want to turn it on. Of course, you expect it simply to work but, unfortunately, this is not always the case.

Air conditioning freezing up is one of the most common issues you can get. There are several possible causes and it’s advisable to know what these might be.

However, you should note that air conditioners contain refrigerant which is dangerous if handled incorrectly. Make sure you have the number of a specialist in air conditioning in Sydney before you start looking at your machine; you may need their help.


An air conditioning actually uses the warm air from your home to keep the coils from freezing up! They will freeze if the air is too cool as the water cannot exit the unit properly.

As it’s unlikely that you’ve turned the air conditioner on while it’s cold outside, the most likely cause is an air flow issue.

You’ll need to check the vents and pipes that take warm air out of your home and to the unit. You will also have registers which need to be open; allowing the air to flow.

Dirty Air

The same check should highlight if there is an issue with your vents and air filtration system. If these are dirty they can be blocking the flow of air and place excess strain on your machine; potentially causing it to freeze up, or even overheat!

Low Refrigerant

It is also possible that the refrigerant level in your unit is too low. If this happens there is insufficient refrigerant to take the heat out of the air, leaving the coils cold and likely to freeze.

Don’t forget that once your coils freeze and you keep running your air conditioner, you’re likely to do un-repairable damage to the unit. Specifically, the compressor will be damaged which is the most expensive part of any air conditioning unit.


If your thermostat is not working properly then the air conditioning unit may not be turning on and off when it should be. This can result in it in overcooling or under, potentially causing ice to form in the cools due to the lack of warm air.

Checking your thermostat is relatively easy as you’ll hear it click when you change the temperature setting, and you can compare this to a room thermometer. However, replacing it is more difficult and really a job for the professionals.

Blocked Drains

There are many reasons why the drains can become blocked. You may find that pests have made nests in the vents over the winter months. It can also be a buildup of dirt or even because the coil is already frozen.

If this happens the coil will be frozen as the water has nowhere to drain too. That’s why it’s essential to check the drainage part of the system before you turn it on; especially if it has been off for a period of time.

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