Why Is My Air Conditioner Freezing?

Posted on: 1 June 2015

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So, you woke up this morning and noticed your home was a little stuffy. You took a look at the air conditioner and noticed that some of the coils were covered in ice and frost. Frozen coils are a common problem that air conditioners experience under certain conditions. If you're wondering what the problem is and how to fix it, read on.

Air Conditioner Basics

In order to understand why your air conditioner is frozen, you must first understand how your AC works. It goes like this: freon inside the condenser coils is placed in a low-pressure environment and the temperature of the freon cools. Warm air form your home comes into contact with the freon-cooled coils, and heat from the air is transferred to the freon. The freon is then transported to a location outside the home where pressure on the freon is increased and the freon becomes super heated. The heat from the freon is expelled and the process begins again. 

Reasons Why an AC Would Freeze

In order for the heating and cooling process to work, your air conditioner system needs adequate freon and air flow. There are basically three reasons that your air conditioner might freeze up:

  1. Restricted air flow. If the warm air from the home is unable to reach the cooled air conditioner coils, maybe because of a clogged air filter, then the heat transfer can't take place and the coils freeze. 
  2. Mechanical failure. If your air conditioner blower or some other mechanical part of your air conditioner fails, then the coils may freeze while waiting for the warm air that will never come. 
  3. Insufficient freon. If the freon in your air conditioner is insufficient, the gas will expand more than necessary and the temperature inside the coils will become too cold, which in turn could cause the unit to freeze.

Suggestions for Repair

The first thing you should do when your air conditioner coils freeze is to change the air filter on the unit. If the air flow is restricted by a dirty filter, this could easily fix the problem. On most units, the air filter will be located in a compartment between the return air duct and the blower. Turn off the air conditioner and give it a day to thaw out. While the coils are returning to room temperature, remove the air filter and take it to a hardware store. Use the old air filter to find a matching replacement filter. Back at the house, put the new filter in place and then turn on the air conditioner when the coils have warmed up. If a dirty air filter doesn't seem to be the problem, call an air conditioning repair person, like those at Action Air of Florida, for help.