Jack Nicholson looking like a frozen central air conditioner

It’s the middle of the hottest summer you can remember, you’ve had your AC running at full blast all week long, when all of a sudden you realize that there’s a puddle of water below your air conditioner and you can’t hear the fan. Believe it or not, but the culprit of this AC meltdown could actually be a central air conditioner freeze up. Pop open your AC housing and you’ll likely be greeted with a block of ice covering your AC equipment, which, oddly, isn’t something you want to see in the dead heat of summer.

If your central AC has frozen, it’s time to call in the big guns to solve the problem. But what exactly could be the cause of a central air conditioner freeze up?

What Causes a Central Air Conditioner to Freeze Up Inside?

You’re probably wondering what causes your AC coils to freeze up – and that’s a great question. The smarties will throw around something called the Joule-Thompson effect, which explains the basic physics of your central air conditioner. But (luckily) you don’t need to know what that is in order to determine the potential causes of your frozen central air conditioner.

Possible Causes of a Central Air Conditioner Freeze Up

  • Low refrigerant – the refrigerant does what you might expect – it helps to cool your air. However, when you have a refrigerant leak or low refrigerant, the air pressure lowers. In short, less Freon means lower temperature, which can cause the evaporator coil to freeze, along with all the moisture in the air that touches it.
  • Not enough air getting to the evaporator coil – your evaporator coil is designed to cool hot air as it passes over the coil. If not enough air is getting to your evaporator coil, then the temperature of your central air conditioner will drop, causing it to freeze up.
  • It’s not hot enough outside – your central air conditioner will freeze up if you run it when the weather is relatively cool outside (say, 64 degrees or below). Your AC pressure will get too low, causing freezing temperatures that turn your AC’s insides into a block of ice.
  • Some other mechanical failure – your central AC is a well-oiled machine, and every part plays a role. If one step of the process is interrupted, the result could be a central air conditioner that freezes up. Check for a malfunctioning blower, a blocked refrigerant line, blocked air filter, or other culprit the next time your central air conditioning freezes.

So Your AC Unit is Freezing Up – What’s Next?

So, you know what some of the possible causes are, but what about possible solutions? Here are a few main items to check or have serviced in order to fix your central air conditioner freeze up.

  • Ductwork – if your ductwork gets so dirty that it blocks airflow to your AC, then you’ll definitely run into problems, whether it’s an AC freeze up or worse. Have a professional inspect and clean out your ductwork as needed.
  • Evaporator Coil – if your evaporator coil is dirty, it won’t get enough airflow. This can lead to a musty smell coming from your central air conditioning system, as well as a freeze up.
  • Air Filter – the easiest thing to check is the status of your air filter. Make sure to regularly replace your air filter (at least every three months) to ensure adequate airflow to your AC.
  • Refrigerant Line – if there is a leak or a kink in your refrigerant line, a central air conditioner freeze up is likely inevitable. Have an HVAC professional target and repair the refrigerant leak ASAP.

Make sure to have regular air conditioning maintenance performed to avoid an AC freeze up and keep your home cool all summer long.