What Causes Air Conditioners To Freeze Up?

Unless you’ve been in a kingdom of isolation for the past year, you’ve probably heard of a little movie called “Frozen.” But even if you’ve seen it a million times, I bet you didn’t realize there’s an HVAC lesson to be learned! my-mommy-sings-Frozen

In Frozen, Elsa tries hard to control her power to freeze objects with a touch. But, she accidentally sets off a chain of events that plunges the kingdom of Arendelle from summer into a sudden, brutal winter. At first, she doesn’t know how to reverse what she’s done, but her sister Anna eventually teaches her the secret to bringing summer back to Arendelle.

One of the most frequent questions we get this time of year is “What makes my air conditioner freeze up?” It seems strange to encounter a block of ice in the middle of a hot summer day, even if you aren’t living in a Disney movie! But much like Elsa’s dilemma, there are some common causes – and more importantly, solutions – that are right at your

Elsa’s powers come from her feelings – she takes in too much from her surroundings, and the more sadness or fear build up, the more ice grows around her. In your air conditioner, this relates to the air flow. Dust, debris, dirt, and other particles settle into your unit as the air circulates. Changing your filter regularly is the first line of defense, as air flows more freely through a filter that isn’t clogged with dirt and dust. These particles can also build up inside the coil casing and block the flow of air through the coil. This is one (of many!) reasons why scheduling regular, professional maintenance is a good idea.


Another reason that poor Elsa’s powers got away from her was that she never allowed herself a break from trying to hide her powers – even from her sister. Running your unit constantly when temperatures fluctuate can cause your air conditioner to freeze up. This is especially important in weather like we have had recently, with warm days and cool nights. When you see a forecast in the  80’s during the day, that drops into the 60’s at night, make a note to shut off your air conditioner before bedtime. We get a lot of “phantom” service calls this time of year where a customer reports a frozen coil, but by the time we get there everything is fine. Sometimes it’s because the unit has been running overnight on cool evenings. Check the forecast against the set point on your thermostat and if they’re within about 5 degrees of each other, shut your unit off overnight.

So what should you do if your air conditioning unit suddenly seems to have taken a trip to Arendelle? First, shut the unit off. Running an air conditioner for an extended period of time with a frozen coil can cause major, expensive damage to the compressor. Once you have the cooling unit off, set the fan to “On” and let it run to help thaw the coil. Check your filter and change it if it is dirty or clogged. Then, look back to see if the temperature has dipped below your set point in the past 24-48 hours that the unit has been running. Picture1

If you aren’t able to identify the cause of the freeze up, or if you’ve taken corrective action like changing the filter and shutting off the air conditioner when temperatures drop and you are still experiencing a problem, call one of our air conditioning experts to get you back up and running.

Do you have a question for our HVAC experts? Let us know, let us know! It may be featured in an upcoming post!

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