Why is there ice on my AC lines, and what do I do?

Ice on an air conditioner in 105° weather looks impossible, which is why it panics people. The physics is simple: when the evaporator coil gets less heat than it was designed to absorb, its temperature falls below freezing and the moisture in the air freezes onto it. The two ways that happens are starved airflow and a low refrigerant charge.

Do this first, in order. Set the thermostat to OFF but the fan to ON. That moves warm air over the coil and melts the ice in an hour or two. While it thaws, check the filter; a filter you can’t see light through is the single most common cause, and swapping it may end the story. Put a towel by the indoor unit, because a thawing coil drips.

Do not keep running the system iced. The compressor is being asked to pump liquid it was never designed to handle, and that’s how a $340 problem becomes a compressor conversation.

If the coil re-freezes with a clean filter and good airflow, you’re most likely low on refrigerant from a slow leak, and that is technician territory: leak repairs run $340 to $890 flat depending on location. A tech should find and fix the leak, not just top off the charge. Refrigerant doesn’t get used up like gasoline; if it’s low, it went somewhere, and topping off without fixing the leak just schedules the same failure for later in the summer, at the same price, plus the refrigerant.