$200 OFF Special price for Installation of a replacement Humidifier read more
Our Blog
Deljo Heating & Cooling
3 minutes read

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.

Recent Posts


How Long Does a Heat Pump Last? What You Need to Know

It can be increasingly difficult for homeowners to find energy-efficient and cost-saving HVAC solutions. Fortunately, heat pump systems have become that solution, heating and cooling your home from one central unit. If you have a heat pump, you’re probably wondering how long it will last until you need to replace it. Read this guide to understand the lifespan of these systems, especially when considering a new heat pump installation for your home. The Lifespan of Heat Pumps On average, a...

Read More

What to Do if Furnace Stops Working in Winter

A malfunctioning furnace during winter is a nightmare. Your heating system faces a lot of stress in harsh weather, working nonstop to keep you and your loved ones safe and warm. Read this guide if your furnace breaks or starts blowing cold air with ways to fix it! Check the Thermostat The first thing to inspect is your thermostat. Set the desired temperature in your home and ensure it functions correctly. Sometimes, simply adjusting the thermostat can kickstart your furnace...

Read More

The Simple Winter HVAC Maintenance Checklist

Winter is here, so it’s time to schedule your annual HVAC maintenance visit! As the temperatures drop, your heating and cooling systems must work without risking frozen units, breakdowns, and costly replacements. Read this winter HVAC maintenance checklist to keep your system in top condition. Why HVAC Maintenance is Important Regular maintenance is like a check-up for your HVAC system. It keeps everything running smoothly, improves energy efficiency, and extends the lifespan of your equipment. Neglecting maintenance can lead to...

Read More