What causes an AC unit to freeze up?
A frozen AC unit in a Florida summer looks absurd and is a genuine emergency — ice on the coil means no cooling and often water where it should not be. Here is what causes it and what to do while you wait for service.
Airflow first, always
Ice forms when the coil gets colder than it should because not enough warm air passes over it. The usual culprits: a clogged filter, collapsed or disconnected ducting, closed supply grilles, or a blower motor that is weak or dead. Salt air and heavy pollen loads make filters clog faster in Fort Myers than the filter's rated lifespan suggests.
Low refrigerant from a leak
Refrigerant absorbs your home's heat; when the charge runs low, the remaining refrigerant gets too cold and ices the coil. Leaks show as oily residue at fittings, hissing, or ice that returns within hours of thawing. The leak must be repaired before a recharge — otherwise the cycle repeats.
The blower, the thermostat and the run cycles
A blower motor on its way out, a thermostat that calls for cooling continuously, or very low setpoints on a hot day can all push the coil below freezing. If the unit freezes every afternoon, note the time and the thermostat setting — the pattern helps the technician find it faster.
What to do right now
Switch the thermostat to OFF at the fan position (FAN ON, COOL OFF) and let the ice melt — hours, not minutes. Do not chip at the coil. Replace the filter, make sure every supply grille is open, and if it freezes again after a clean restart, book a visit. Water from the melt can overflow the drain pan, so put towels down under the air handler.
City to City HVAC provides Emergency AC Repair, AC Installation & Replacement, Duct Cleaning & Air Quality, AC Maintenance & Tune-Up across Lee & Collier Counties, Florida.
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