Frozen coil
Ice usually points at the air moving across the coil or at the refrigerant inside it. Turn cooling off first. Running a frozen system is how a repair turns into a bigger one.
Updated August 23, 2026
01
Set the thermostat to off and leave cooling off until the visible ice has melted. Watch for water around the indoor equipment as it thaws. Do not open equipment panels or work on refrigerant or electrical parts.
02
A cooling coil needs a steady volume of warm indoor air across it. Take that air away and the coil keeps getting colder until moisture on it freezes. ENERGY STAR puts filter changes, coil cleaning and blower adjustment on the maintenance list for exactly this reason.
03
Too little refrigerant drops the pressure in the coil, and a coil running colder than it should will collect ice. ENERGY STAR lists checking and correcting the charge as part of a cooling check-up. A charge that keeps dropping means a leak, and topping it up without finding the leak brings you straight back here.
04
Note the outdoor temperature when the ice appeared, what the thermostat was set to and how long the system had been running. A system that ices only on a cool night is a different conversation from one that ices in the middle of a hot week. Those details narrow the search before anyone opens a panel.
05
A filter, a blower, a crushed duct, a dirty coil and a refrigerant leak can all produce the same sheet of ice. That's why a frozen coil is a symptom and not a diagnosis. The useful next step is finding out which one it is, not replacing the part that gets replaced most often.
06
When the ice appeared, where it is, whether it came back after thawing, what the filter looks like, which rooms feel weak and any water you found. That is enough to start. You don't need a model number, though it helps when it's easy to reach.
Common questions
Yes. Turn cooling off and let the ice melt completely. Running the system with a frozen coil risks damaging the compressor, and a frozen coil is not going to cool the property anyway.
It depends on how much ice formed and how warm the space is. Keep cooling off until all visible ice has melted. If the ice comes back once the system runs again, the cause is still there.
Not by itself. Low refrigerant is one cause. Restricted airflow from a filter, a coil, a blower or the ducts is another. Adding refrigerant to a system that is losing it leaves the leak in place.
Primary sources
