Every July we get the same confused call: there is ice on the copper lines outside, or a sheet of frost on the indoor coil, while the thermometer reads 110. It seems backwards, but ice is one of the most common cooling failures in Arizona, and it always comes down to one of two causes.
Cause One: Starved Airflow
Your indoor coil needs a steady river of warm house air flowing over it. Restrict that river and the coil gets colder and colder until humidity freezes onto it. The usual suspects:
- A clogged air filter, the number one cause by far
- Closed or blocked supply vents in unused rooms
- A failing blower motor that cannot move enough air
- A coil coated in dust that insulates it from the airstream
The fix can be as simple as a new filter and a few hours of thawing with the system off and the fan running. Our Arizona filter guide explains why desert homes need changes far more often than the box suggests.
Cause Two: Low Refrigerant
Refrigerant pressure and temperature are linked. When the charge drops from a leak, the coil runs colder than designed and ice follows. The tell: you thaw the system, it works for a day or two, then the ice returns. That pattern means a leak, and topping off without fixing it just rents you a week of cooling. Our leak detection service finds the actual failure point.
What to Do Right Now
- Switch the thermostat from COOL to OFF, but set the fan to ON. Moving air speeds the thaw.
- Check and replace the filter while you wait.
- Give it two to four hours. Running the AC while iced can kill the compressor, the most expensive part in the system.
- If ice returns within days, stop thawing and book a diagnosis. Typical repair costs are in our cost guide.
Not sure which cause you have? Call 480-406-7487 and describe what you see. We can usually tell you over the phone.