In this short Q&A, Derek Cole explains that the most common reason an air‑conditioning unit freezes is insufficient airflow. He outlines three primary culprits: a dirty or blocked air filter, a dust‑laden indoor blower wheel (the “squirrel cage”) that loses its ability to push air, and leaks in the ductwork that can waste 20‑30% of the airflow according to EPA data. Cole advises homeowners to inspect and replace/clean the filter, remove the blower wheel, clean it thoroughly (spray, dry, and reinstall), and seal any duct leaks. He emphasizes that if the system feels off, a visual check is the first step, and recommends calling a professional when needed.
Chapters
What causes my unit to freeze over in cooling?
A couple things could be happening when that goes on. The main cause is usually airflow. So you need to check your filter to make sure that it's clean, it's been replaced, it's not stopped up, that way air cannot get through. And another thing is when you have a dirty unit, a dirty indoor blower motor and a dirty wheel, see what happens. When you have the blower motor, which pushes the air in the house, right? So that pushes the air in the house and uses what's called, we call a squirrel cage, but it's a blower wheel that actually pushes the air in. So if you look at the blower wheel, it's kind of like a cup. It has all these little fins on it all around the circle and it's taking air and it's throwing it and it's pushing it. All right, it's pushing it in the house. So when that becomes dirty, when you have a dirt and a dust buildup on it,— it becomes flattened. So now you're trying to push air like this. Obviously not as effective as the cup, right? So one thing to look at is make sure your unit is clean. We go to quite a few systems where our blower wheel needs to be taken out, taken outside, cleaned, sprayed down, dried off, and then put back inside because there's so much of a cake of dirt and dust on that blower wheel that it's gone from a cup to straight and therefore it's not catching the air, it's not throwing it back in the house. Outside of that, in the freezing unit, check your duct system to make sure that's happening as well. Again, the EPA says that 20 to 30% of your duct air loss is from the duct system because of leaks. Make sure all that is sealed up. Again, when that air cannot— anymore, when the air cannot get through to the inside of the house to the duct system, that's going to cause an airflow problem. So make sure your unit is clean, make sure your duct system is sealed, and make sure you don't have that freezing going on with your system. So if something feels off, if something feels like it's not normal, you know, go out there and just kind of look it over, check it out, see what's going on. And always, you know, call us if you need us.
