Do this first
Turn cooling off at the thermostat and set the fan to on. That lets warm room air thaw the coil. Do not chip at the ice, and do not keep running the system in cooling while it is frozen, because liquid refrigerant reaching the compressor is how a repair becomes a replacement.
Cause one: not enough airflow
The evaporator coil gets cold and relies on a steady flow of warmer room air across it. Restrict that flow and the coil drops below freezing and condensation turns to ice.
- A clogged filter, the most common cause by a distance.
- Blocked or undersized return vents.
- A failing blower motor.
- A duct system that cannot move what the equipment needs.
- A coil already dirty enough to restrict flow itself.
Cause two: low refrigerant charge
Low charge drops the pressure in the coil, which drops its temperature below freezing. Since refrigerant is not consumed, low charge means a leak, and topping it up without finding the leak puts you back here.
Ice on the outdoor unit in winter
Different situation. Heat pumps frost up in cold weather by design and run a defrost cycle to clear it. A unit encased in ice, or one that never clears, points at a defrost control, charge or airflow problem.
Why it matters
Ice is never the disease. Clearing it without finding the cause means it returns, and each cycle risks the compressor.
Common questions
Why is my AC frozen?
Either not enough air is moving across the coil, or the refrigerant charge is low. Those are the two mechanisms, and a diagnostic separates them.
Should I turn it off?
Yes. Switch cooling off and leave the fan on so the coil thaws. Running an iced system risks the compressor.
Can I just melt the ice and carry on?
It will freeze again. Ice is a symptom, so the cause has to be found.
Is ice on my heat pump in winter normal?
Some frost is, and the defrost cycle clears it. A unit encased in ice that never clears is not normal.
Reviewed and updated September 2026. Prices shown are owner supplied typical ranges, confirmed after an assessment. If anything here looks out of date, call (615) 400-4993 and tell us.