AC Freezing Up in Dallas: Why There's Ice on Your Unit in 100° Heat

The indoor evaporator coil runs cold, around 40°F, with a steady stream of warm house air blowing across it. That airflow keeps the coil above freezing. Cut the airflow with a clogged filter, a dirty coil, closed vents, or a weak blower, and the coil drops below 32°F and ice forms.

Low refrigerant does the same thing from the other side. With less refrigerant, the pressure in the coil drops and it runs colder than designed. A slowly leaking system freezes more and more often as the charge falls.

DFW humidity makes freeze-ups worse and wetter. There's more moisture to freeze, and when it melts the condensate drain has to handle a flood.

Set the thermostat to OFF for cooling and FAN to ON. The blower moves warm air across the coil and melts the ice, usually within one to three hours. Don't chip at ice on the coil or lines.

While it thaws, replace the filter and open every supply vent. Closed vents in unused rooms are a common cause of freeze-ups in two-story DFW homes with marginal ductwork.

Watch the attic. As the ice melts, the drain pan and line have to carry a lot of water at once. If the pan overflows, the drain is clogged too, which is common. Put a container under the secondary drain outlet if you can see it dripping outside.

If the system freezes again within a day of thawing with a clean filter and open vents, stop running it. Repeated freezing points to a refrigerant leak, a failing blower motor, a dirty evaporator coil, or a stuck expansion valve, each of which needs diagnosis with gauges.

Running a system that keeps freezing is expensive. Liquid refrigerant can flood back to the compressor and destroy it.

LocalFixQuotes can match you with TDLR-licensed DFW technicians who handle freeze-up diagnosis routinely. We're a free matching service, not the contractor.