What Causes An Air Conditioner To Freeze Up?

What Causes An Air Conditioner To Freeze Up

Not too long ago, I had the air conditioner on full blast and was typing away, doing what I always do. Then I heard a loud grinding noise. I turned to my air conditioner and realized that the air conditioner had been partially frozen. I was floored. How did this even happen? Would I need to call my landlord and say I busted the AC?

There are several different issues that can cause an air conditioner to freeze up. The most common problems include:

  • Low refrigerant
  • A bad thermostat
  • Closed supply vents
  • A dirty filter
  • Bad drainage
  • Improperly angled window units

Understanding why your air conditioner could freeze up can help you learn how to extend your AC unit’s life. If you’re like me and rely on some good airflow to keep yourself focused, understanding the ins and outs of what causes an air conditioner to freeze over is a must.

Why Is My Air Conditioner Frozen?

There are so many different answers to this question, and all of them are possible reasons for this to happen. To help you troubleshoot your air conditioner woes, we decided to group it by the easiest to the most difficult issues to solve. Hope it helps!

Easy Fixes

Before you start to panic, try these quick troubleshooting moves below. They are easy enough for anyone to do, and can often fix a slew of problems. Prior to doing any of these items, make sure that you’ve turned off the unit and let the ice melt.

  • Check to see if your window unit is angled properly. If your window unit is frozen, check the angle. Your window unit should just straight outwards with a slight downward droop towards the outside. Having a unit that’s too heavily tilted forward or evenly balanced could actually harm your machine.
  • Open up your unit and clean the filter. If there’s one thing that we’ve shown in every article so far, it’s that having a dirty filter will wreck any type of HVAC equipment that you could potentially have. Once you clean the filter, let the unit sit for a bit and then turn it on again. Chances are you won’t have an issue anymore.
  • Open your supply vents. Are your supply vents closed? That’s bad because that traps the cold air inside and potentially freezes up things inside your AC unit. The end result? A frozen air conditioner that’s making some fairly funky noises.
  • Use a hairdryer to melt your coils if you think they’ve frozen solid. Even if you waited for your AC to melt, it’s important to try to heat the coils a little extra. Frozen coils will make your AC unit fail sooner rather than later.
  • If your unit has a drainage system you can access, check the drainage. Check your unit’s condensate drain to see if it’s blocked. You can usually tell if it is through issues like standing water in and around your unit. If it is, wait until the ice melts, remove the excess water with a shop vac (or rag), and clean out the drain so that water can leave the unit properly.

Medium To Hard Fixes

If you’ve cleaned out the vents, done the drainage thing, cleared your filters out, and even checked to see that your unit’s been angled the right way, you may still have some troubleshooting to do. These steps can be a bit tricky, particularly if you don’t know your way around an air conditioner.

With these tasks, there’s no harm in asking for professional help if you need it. As with the last batch of troubleshooting moves, you should do these after you’ve turned off the unit and let the ice melt. Here’s what could be causing the icy buildup.

  • The first thing you should do is to check the unit’s refrigerant levels. Believe it or not, your unit’s refrigerant levels are the most likely culprit of a unit that keeps freezing over. Low refrigerant levels will make your unit’s coils run cold. This, in turn, causes ice buildup over time.
  • Then, check your unit’s fan. An improperly working fan will prevent air from flowing in your unit properly. This, in turn, traps cold air until it becomes at risk for freezing. It also can make your AC run warmer than it should. If your AC unit’s fan motor blew, then you need to call a professional to get it replaced.
  • Check your AC unit’s thermostat. Sometimes, a bad air conditioning thermostat can cause your unit to be unable to register the temperatures that are present around the unit. This, in turn, can cause your unit to freeze over by accident.

Can I Pour Hot Water On A Frozen Air Conditioner?

If you have a frozen air conditioning unit, you probably are curious about whether or not you can pour warm or hot water to help it thaw out. There’s some good news here. If you’re in a rush to get your AC unfrozen, you can pour hot water on the unit without worrying about thermic shock breaking most of the parts.

AC units are built to withstand severe weather fluctuations, so temperature changes won’t be that big a deal. Moreover, AC units are used to having water running through many of their parts. As a result, the water pouring trick won’t harm your unit.

How Long Does It Take To Thaw Out An Air Conditioner?

Obviously, thawing out your AC unit is going to be the first step you’re going to have to do before you can really start troubleshooting. To thaw your unit out, you are going to have to turn it on and keep it in a temperature that’s above freezing. It can take anywhere from a single hour to up to 24 hours for your unit to fully thaw out.

How long it takes depends on the level of frost that you’re dealing with as well as the build of your air conditioning unit. To be on the safe side, it’s best to wait for at least four hours before you start tinkering around with your unit.

Can I Run An AC Unit With Frozen Coils?

It might be a little tempting to try to keep your unit running, even when you see coils that seem frozen. Believe it or not, you technically could keep your unit running. However, you shouldn’t do it for a wide range of reasons. You might not actually get any cold air into your home if you do, and to make matters worse, doing this will cause serious problems with your compressor.

Since your compressor is the most expensive part of your AC system to fix, we strongly advise against doing anything that could harm it.

When Should You Call A Professional To Fix Your Air Conditioner?

Most of the issues that cause air conditioners to freeze can be fixed through casual DIY approaches, or even through the help of a YouTube how-to video. However, we’re going to have to be honest here. Not everyone should be doing their own AC repairs, nor should they always be the ones to try to do them.

Air conditioners are expensive, especially if you’re doing central air. In order to avoid causing bigger problems than what you initially started off with, call a professional whenever you feel “in over your head.” It’s smarter to pay a fee rather than risk making a wrong move. Who knows? If you hire the right person, they might even teach you how to fix it yourself.

Can High Humidity Levels Cause Your AC Unit’s Coils to Freeze Up?

Though it’s very rare and usually will only happen on cold, rainy days, it is possible to have humidity cause your coils to freeze up. The cold water condensation around your coils can encourage the growth of ice crystals, which will freeze your entire unit over within the course of its use. If you need to get some cooling during humid times, try other methods before you resort to your AC.

Related Questions

How often should I clean (or replace) an air conditioner filter on a window unit?

While this can vary based on how frequently your AC unit is turned on, the truth is that most units will need a cleaning at least once a month. If you use it every day or smoke inside your home, doing a weekly cleaning is more advisable since your filter will be more prone to catching dirt in the air.

How can I tell if my AC’s drain line is clogged?

Along with having a portion of your unit get frozen, you can tell that an AC unit’s drain line is clogged up through a number of symptoms. You might notice a musty, almost urine-like smell from your unit. You also may notice that your unit isn’t turning on, or if it is, you may notice that your unit isn’t actually cooling your home. Standing water or piles of leaves near the line can also indicate a clog.

What is dirty sock syndrome?

Dirty sock syndrome refers to the issue of having a mildewy, musty, sock-like smell that emits from air conditioners. This usually happens after mold or mildew grows in the AC unit’s vents. This is a syndrome that is connected to having high humidity in your home as well as having your air conditioner freeze over.

To get rid of the “dirty sock” smell, you will need to clean your AC unit and wash the filters as well. To prevent regrowth, make sure that you take the time to use bleach or a mildew-killing cleaner to make the area inhospitable for mold.

Ossiana Tepfenhart

Ossiana Tepfenhart is an expert writer, focusing on interior design and general home tips. Writing is her life, and it's what she does best. Her interests include art and real estate investments.

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