Why does an air conditioning unit freezes up?

This is a common problem amongst air conditioners owners. Below yo can find some details on the problem and some ways to rectify it.


One common cause is dirty filters.

This will make the unit work harder, because the air can’t get through the filter. This will cause the air conditioner to ice up. So the first thing to do is to check the filter and replace it if you see that it’s dirty.


Another cause of freezing air conditioners is the low-level of refrigerant. This may be the cause of a leak or of a human error. Either way you should call a professional and have him check the system for leaks and refill the system with refrigerant.

Air flow

If your system has poorly designed duct work, then this may be an airflow issue. If the ducts are too small, the air will struggle to blow across the fan coil, causing the unit to ice up. You can see if this is the problem if you can hear the air making a whistling sound.


The outdoor temperature influences the way the air conditioner works. If the temperatures are extreme the unit may struggle to maintain a certain temperature.

Controller temperature

If you set the controller temperature to the maximum settings, you will make the unit work overtime and may cause the coil to ice up.


Many air conditioning units have been designed to run only half of a house at once. If you have a system like this, then make sure you do not run too many zones at once.

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