Why humidity makes it worse
- Humid Louisiana air carries a lot of moisture that condenses on the coil. When airflow drops, that moisture freezes on the coil instead of draining, and the ice blocks the rest of the airflow. It snowballs.
- A system that is slightly low on refrigerant can run fine on a mild day and ice over on a humid July afternoon.
The safe thaw
- Set the thermostat to Off for cooling and Fan to On. Do not chip ice off the coil.
- Put towels under the indoor unit. Thawing ice produces more water than the drain pan expects.
- Replace the filter while it thaws. Open any closed supply vents.
- After one to three hours with no ice, set it back to Cool. If it freezes again within a day, stop and call.
What a technician looks for
- Refrigerant level and a leak search, since low charge is the most common cause after airflow.
- Blower motor and capacitor, coil condition, duct restrictions and the condensate drain.
- In older New Orleans houses with attic air handlers, undersized return ducts are a frequent reason a system never gets enough air.
General guidance from the U.S. Department of Energy on home air conditioning. A diagnosis by a technician is the only way to know what your system needs.