Ice on an air conditioner feels backwards — isn't cold the point? — but a frosted coil or an ice-wrapped copper line is a system in real distress, and the single most important instruction fits in one line: switch cooling OFF (fan ON is fine) and let it thaw before anything else. Running a frozen system floods liquid refrigerant back at the compressor, and that's how a modest problem becomes a compressor obituary.
Why coils freeze: only two roads lead here
Road one: starved airflow. The indoor coil needs a steady river of warm house air flowing over it; choke that river and the coil's temperature dives below freezing, humidity in the air becomes frost, frost blocks more airflow, and the spiral feeds itself. The chokers: a filter loaded to felt, a failing blower motor, crushed or undersized ducts, or a coil face matted with years of dust.
Road two: low refrigerant. A leaking system runs its coil at lower pressure, and lower pressure means lower temperature — below freezing, same spiral. The tell that separates the roads: airflow problems usually freeze the coil face broadly, while low charge often ices the suction line and coil even with a clean filter and strong blower. Gauges settle it definitively.
The melt-out, done right
Cooling off, fan on high, towels under the air handler (a big coil holds a surprising amount of ice — that water goes somewhere), and patience: hours, not minutes. Don't chip at it; fins bend and coils puncture, converting road one into road two. Once thawed, replace the filter and try a cycle — if freezing recurs with a clean filter and good airflow, stop running it and get the charge checked; you're on road two, and road two means a leak to find (see our refrigerant leak guide).
The Pacific Northwest wrinkle
Our ACs sit idle nine months, then sprint through a heat wave — and a filter that seemed fine in April is loaded by the July week everything runs flat-out. Half the frozen coils we thaw around Bothell and Everett trace to exactly that. A pre-season filter change and coil check is the cheapest freeze insurance that exists.
Our part
We meter the airflow, gauge the charge, name the road you're on, and fix it on a written quote — and if it's road two, you'll get the leak's actual location, not a seasonal top-off subscription.