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Why is my AC's evaporator coil frozen?
Ice on your coil is a symptom, not the disease. It's almost always one of two things: not enough air moving across the coil (dirty filter, weak blower, closed vents), or not enough refrigerant (a leak). Either way the coil runs colder than designed, so the moisture condensing on it freezes instead of draining away — and the ice then blocks the airflow completely, making it worse.
What causes it
Almost always a symptom of something else: low airflow (dirty filter or weak blower) or low refrigerant.
What it does to the cycle
Ice encases the coil and blocks the airflow completely, so cooling stops and the melt water can overflow the drain pan and leak.
What you'd notice
Visible ice on the coil or lines, water pooling around the indoor unit, and no cold air at all.
What to do about it
- Set the thermostat's cooling to OFF but switch the fan to ON. Room-temperature air melts the ice fastest.
- Wait 2–4 hours; a thick block can take most of a day. Never chip or scrape the ice — you'll puncture the coil.
- Put towels down. A surprising amount of melt water comes off, and the drain pan can overflow.
- While it thaws, change the filter and open every supply vent in the house.
- Restart cooling. If it freezes again, you almost certainly have a refrigerant leak — that one needs a tech.
The bottom line
Switch cooling off and run just the fan to thaw it (a few hours), then fix the root cause — change the filter or call a pro for the leak.