What Causes an Air Conditioner to Freeze Up?

It almost seems counter-intuitive that an air conditioner could freeze over, especially when your air conditioner is running during hot summer days. Air conditioner freeze-ups are actually quite common and there are a number of possible culprits. Below are 4 of the most common causes of an air conditioner freeze-up. 

Blocked Airflow

Air conditioners need to have constant airflow so humidity doesn’t settle on the coils and freeze. This humidity can even collect in dry climates like Colorado. Here are the common culprits of a lack of airflow in an air conditioner:

Dirty Filters

If your air filter is dirty and becomes clogged, airflow is restricted which disrupts your air conditioner’s functionality and increases the risk of an air conditioner freeze-up. Thankfully, air filters are inexpensive and keep your air conditioner running at peak performance, saving you money on your electricity bill. You should be changing your filter every month even if it says every three months. 

Closed or Blocked Vents

Closing or blocking too many vents in your home is a quick way to cause an AC freeze-up. If you have something in front of a return, you want at least 6 inches of space. If you decide to close some of the vents in your home, make sure they are not near your thermostat and you are only closing a few. 

A lack of airflow can also be caused by a collapsed duct, a bad blower motor, or low voltage to the fan, so if your filter is clean, you are not blocking your vents and you are still experiencing AC freeze-ups, contact an HVAC expert as soon as possible.

Overworking the System

This means a consistent runtime of more than two hours. Here are the two most common ways to overwork your air conditioner:

Setting the Temp Too Low

If you set your temperature too low and your air conditioner can’t keep up with the heat load, it will freeze over. You are making your air conditioner try to change the temperature of a large area too quickly, making it run longer than two hours. Make sure you lower your thermostat slowly to give your system a break, and don’t forget to rely on your other appliances like fans to cool the air as well. 

Cool Weather

For places like Denver where the Spring and Fall seasons bring warm days and cool nights, it’s not uncommon to have an AC freeze-up when your home is a lot warmer than the temperature outside. Air conditioners are designed to function in a specific temperature range. If you are running your air conditioner for more than 2 hours when the outside air is below 62 degrees, the pressure inside of your system will drop causing your air conditioner to freeze up. Try not to rely on your air conditioner when it’s cooler outside.

Dirty Coils

Another common cause of AC freeze-ups is a dirty air conditioner coil. Air conditioners tend to dehumidify the air, and that moisture builds up on the condenser coils. When the water builds up on clean coils, it evaporates or falls into the drip pan. If the coils are dirty, that layer of dirt and dust holds onto the water causing a freeze. Bi-annual checkups from your local HVAC professional can keep your AC’s coils clean.

Low/Leaking Refrigerant

In order for the refrigerant in your air conditioner to absorb heat and cool the air, it transitions from a low-pressure gas to a high-pressure liquid and back to a low-pressure gas. If there is a refrigerant leak or the refrigerant is too low, this causes a drop in pressure allowing the refrigerant to expand more than usual and become too cold. If there is a refrigerant leak, an HVAC expert can help you fix this but may recommend investing in a new air conditioner.

Though these are the most common culprits of an air conditioner freeze-up, there are a variety of other things that could cause this problem. If you are in Aurora or anywhere throughout the Denver Metro Area, Grand Home Services would love to help you with your air conditioner maintenance, cleaning, repair, or replacement needs. Contact us today!