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Why Does my AC Keep Freezing? 

Published by Luke Weiden

At Deljo Heating & Cooling, the company providing the very best air conditioner repair in Chicago, we know it’s a very common occurrence for ACs to freeze up, turning a beautiful summer day into a sweaty nightmare.

Some simple physics

To understand this problem, we’ve got to know a little high school physics, and we promise to keep it simple!

The basic principles of thermodynamics say that as gas expands, its pressure and its temperature decrease. Likewise, as it is compressed, its temperature rises.

Basically, your AC works by allowing the evaporator coil to expand the refrigerant inside it, causing the coil to cool. As your system blows warm air from your home over the cooled coil, the refrigerant absorbs the heat from the air inside your home.

The heated refrigerant is then transferred outside where it’s compressed, releasing the heat into the outside air.

This cycle repeats itself over and over, cooling your home in the process.

However, if something malfunctions to interrupt this cooling/heating/cooling cycle, the entire system is disrupted, and the evaporator coil allows the refrigerant to cool too much, and that leads to freezing and icing over.

The causes and things you can do

There are several things that can cause your system to freeze over, and some of these you may be able to fix.

1. Blocked air flow

An AC system has to have a constant flow of air to prevent humidity from settling on the coils and freezing. If this happens, dirty, clogged air filers may be the cause.
Turn the system off for 1-3 hours to let it thaw and replace the dirty filters. Restoring the normal air flow may resolve the problem.

2. Cool nighttime temperatures

ACs are designed to run within a given temperature range, and if you’re running your system when the outside temperature is below 62° the pressure inside the system will drop, causing your system to freeze up. In that situation, turn your system off.

3. Low refrigerant or mechanical problems

If the refrigerant level is too low, or there is a mechanical issue like a broken blower fan, those things can change the pressure in your system and cause it to freeze up.

In cases like that, it’s best to call in the experts from Deljo Heating & Cooling, and we’ll have your system back up and running in no time at all.