Why is My Air Conditioner Frozen?

Frozen AC Unit Coils is Not a Good Thing

Your home air conditioning system cools your air, and makes your home a place of comfort. Many people take a look at their indoor air conditioner, and notice that the coils are frozen. They may believe this means the air conditioner is really working well.

But that’s a mistake that can lead to costly repairs.

why is my ac unit freezing up

The science behind frozen AC coils

Let’s make it clear from the beginning. frozen parts on your air conditioner mean something is wrong. Not right. Not better than it used to be.


Frozen air conditioning coils mean that there is something wrong with the system, which is causing a temperature imbalance within the refrigerant flowing through the inside evaporator coils. There may not be enough warm air or heat moving over the coil, or the refrigerant is not doing a sufficient job at absorbing heat.

If ice is coating the coil, the air conditioner simply will not function as well as it should. The ice acts as an insulator, preventing the refrigerant from absorbing heat and cooling the home. The way hot and cold works is really a measure of heat, and only heat. Heat is removed from a material (air, metal, water, etc.) and that registers with our senses as “cool”. This heat transfer is what “cools” your home. The refrigerant removes heat from the air as the air passes over the coils. Ice blocks the surface of the coil, and prevents the refrigerant from doing its job.

So, what’s causing ice on my coils?

Air conditioners with frozen pieces are a problem, not an indication of hyper-effectiveness. If your air conditioner has parts that are frozen, you really should call an air conditioning services specialist. Some reasons why air conditioners might freeze up include:

Broken fan motor

The fan in your air conditioning system is intended to move enough warm air over the coils to allow the refrigerant to absorb the heat. If the fan is not working, there will not be air flow over the coils, the refrigerant will be looking to absorb heat from what air there is, and ice will form on the coils.

Dirty air filter

A dirty air filter will reduce air flow, and this causes the same result as if you had no fan at all. The reduced air flow will cause the coils to ice up.

Short cycling

Perhaps the air conditioner is too large for the space. If it cannot pull enough air from the small space to counter the cooling effects of the refrigerant, and turns off shortly after turning on, there will be too much cooling, disproportional to the volume of the air. This will cause that troublesome temperature differential, which is the root cause of ice on the coils.

Low refrigerant

It does seem oxymoronic and counterintuitive, but low refrigerant levels could actually cause your air conditioner to stop heat-absorption and heat-release, which will also result in freeze-up.

Can I fix a frozen AC system myself?

If the problem is related to the air filter, then generally speaking, that is simple enough for many homeowners to handle on their own. But what if that was not the problem. An air conditioning repair technician has specialized diagnostic tools and methods to determine the root cause of the freezing, and can replace or repair the parts causing the problem in less time. This also keeps you from spending the time and trouble trying to track down the problem on your own. Another aspect is that refrigerant is a controlled product, and your local air conditioning service agent will be licensed to handle and apply it to your system. If the problem is stemming from low refrigerant levels, that means that there is a leak somewhere in the system. Your technician will, at the same time, be able to locate and seal the leak, to prevent further trouble with your system. So, if you want the best, lasting results, it is always best to call an air conditioning services technician team, to get the fix that sticks!

Metro Express Services is ready to help when you call! There’s no sense sitting in the summer heat when your air conditioner is acting out; give us a call today!


Randy Murphy

Randy Murphy has been building his knowledge of the air conditioning and heating business for several years now. He first started applying his knowledge while working for his father’s HVAC company. Later, in 1987, Randy started his own business: Metro Express Service. He has been a top 10 Trane & Amana dealer for over eight years. When it comes to heating and cooling, Randy knows the business better than anyone.
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