Your air conditioning system needs multiple things to work together correctly. When something is not working correctly, be it with the pressure, airflow, or temperature, the refrigerant system that drives your air conditioner can overwork itself and freeze, creating ice on your unit.
#1: Not Enough Airflow
One of the common reasons your air conditioning unit freezes up is a lack of airflow. There is a wide range of issues that can cause airflow issues. Air needs to flow over the coils to keep them warm and prevent freezing.
You could have a collapsed air duct that is blocking the flow of air over the coils. In this case, the air duct would need to be repaired. Or you could have a bad blower motor, which isn't blowing air fast enough to cool off the coils. Or you could have a fan that doesn't have enough voltage to power the blower fan, resulting in it being underpowered. Or you could have a clogged air filter.
#2: Dusty Coils
Second, it is essential to keep the coils on your unit clean. When dust builds up on the coils, it doesn't just make the coils dirty; it creates a blanket on the coils that act as an insulator. That dust insulates the coils, which then traps the cold inside the coils instead of releasing it. This can result in freezing around your coils and turn your coils into an icebox as moisture and ice build up. This can be solved by changing the air filter on time and keeping the coils on your unit clean.
#3: Low Refrigerant
Finally, your air conditioning unit may be freezing up because you don't have enough refrigerant in the system. This can happen when you have a leak in your refrigerant system, as the refrigerant is designed to stay within the system.
When you don't have enough refrigerant in your air condition system and the warm air converts the liquid refrigerant into a gas, there will not be enough pressure in the system. That cold will then freeze any moisture on the coils instantly. As this flash-freezing process repeats over time, more air will build upon your unit. This can be fixed by fixing the refrigerant leak and then tapping off the unit's refrigerant.
If you have lots of ice on your air conditioning unit, then you have an issue. An experienced air conditioning repair technician will figure out what is causing the ice to build up and fix the problem. Reach out to a professional who provides air conditioning services to learn more.