Your AC unit can freeze solid in summer. A clogged filter blocks airflow over the coils, or low refrigerant does the same thing. Either way, ice forms on the coils and lines, sometimes visible outside or in the attic.
Chapters
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. If airflow is restricted in any way, it's going to cause that to freeze over. You'll see kind of like what happens in your freezer when you have too much ice going on there, right? You see that frozen over coil. Same thing happens with your unit. Another thing could be happening, especially when you go into cooling season, that you'll notice is it's low on refrigerant. But if you're low on refrigerant, it will also tend to freeze over. And you'll start seeing that at the outdoor unit, that little line that goes from the outdoor under your house or in the attic, you'll start seeing that freeze over.