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MrCool, Why is My Air Conditioner Frozen?

air conditioner frozen

Every summer some unlucky schlub wanders outside, slips on some ice, and says, “Hey! Why the heck is my air conditioner frozen? It’s burning up out here!”

Yes, it’s weird and completely counter-intuitive. How could ice build up on your air conditioner in the middle of a hot July?

Don’t freak out. It’s science.

So, Why is My Air Conditioner Frozen, Exactly?

Ice can build up on your air conditioner for two main reasons:

1. Low refrigerant charge.
2. Blocked airflow.

Let’s tackle each one like a Notre Dame linebacker.

Low Refrigerant

Air conditioners depend on super cold refrigerant in order to efficiently transfer heat from the inside of your house to the outside.  Ice can build up when that refrigerant gets too low. However, this isn’t the most common answer to the questions.

Airflow Problems

The main reason why air conditioners turn into ice machines is due to air flow problems. An air conditioner needs constant air flow to work properly. If that air flow gets interrupted or restricted, even by a dirty air filter, ice can start to build up on the coils. As you might suspect, a frozen air conditioner isn’t exactly the best way to keep your house cool in summer.

Fix the Frozen Air Conditioner Problem

So, how do you fix it? Follow these simple steps:

1. Cut the power to the air conditioner. It needs to be 100% OFF.
2. Let the ice melt naturally. This shouldn’t take too long in hot summer weather.
3. Make sure nothing is restricting the air flow around the condenser, the air handler, or inside your ductwork. If you find obstructions, remove or repair them.
4. Change the air filter, and make sure the evaporator coils are not too dirty. A filthy coil could have been the source of the problem.
5. Once the ice is all nice and melted (i.e. – completely gone), turn the unit back on.

Does it work? If it does, you’re probably okay. If it doesn’t, you’re going to need professional help. Contact an HVAC technician to get the unit serviced.

2 thoughts on “MrCool, Why is My Air Conditioner Frozen?”

  1. Hi, I have the 3rd generation 24000btu unit and it’s frozen over and dripping and making a rattling noise. We literally just got it 3 weeks ago. Is this a normal malfunction thats common? We checked and don’t have any blockages and it’s brand new so nothing should be low like the refridgerant. Please help. What’s going on with this?

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