What Causes an Air Conditioner to Freeze Up?

There are several conditions that can cause a central air conditioner’s evaporator coil to drop below freezing, causing the air conditioner to freeze up. When this happens the air conditioner will not only stop cooling properly, it can cause damage to the unit. Here’s what to check if the AC unit is freezing.

1. Lack of air flow. An air conditioner works by taking the heat from inside the home and blowing it over the evaporator coil located outside the home. This split-system enables the heat exchange performed by the refrigerant to take place. Without the exchange of warm air the temperature of the coil will continue dropping, increasing the likelihood of a freeze up.
2. Low refrigerant levels. As the level of refrigerant drops, so does the pressure inside the system. When a smaller amount of refrigerant is forced to expand the same amount, it lowers the temperature.
3. Low outside temperature. If an air conditioner is run when the outside air is too cool, the pressure inside the unit can drop, causing a freeze up. This can occur at temperatures of around 62 degrees.
4. Malfunctioning mechanical systems. A damaged refrigerant line, broken fan, even a clogged up air filter, all can cause the evaporator coil to freeze up.

Have a freezing air conditioner? Call ABC Southwest Plumbing & Air Conditioning. We can help.