Short answer: an AC freezes up when the indoor coil gets too cold, usually because not enough warm air is moving across it or the system is low on refrigerant. Turn cooling off and run the fan only to thaw it, replace the air filter, and if the ice comes back, call a licensed pro.
Signs your AC is freezing
- Ice or frost on the copper refrigerant lines at the outdoor unit or near the indoor unit.
- Weak airflow from the vents, or the AC is blowing warm air.
- Water around the indoor unit as ice melts, which can look like an AC leaking water.
- The system runs constantly but the house will not cool down.
How to thaw it safely
- Turn cooling off at the thermostat.
- Set the fan to On so warm indoor air moves across the coil and melts the ice faster.
- Wait. A heavily iced coil can take several hours to thaw fully.
- Watch for water. Melting ice can overflow the drain pan, so put towels down and check the drain is flowing.
Never chip or scrape the ice off. The coil and lines are easy to puncture, and a refrigerant leak turns a free fix into an expensive one.
Causes you can check yourself
- A clogged air filter. The most common cause. Replace it before restarting.
- Closed or blocked vents. Furniture, rugs, or closed vents in unused rooms starve the system of airflow.
- A blocked return. Keep the large return grille clear.
- Very low thermostat settings. Setting the AC far below the usual range for long periods can contribute, especially on cooler nights.
Causes that need a pro
- Low refrigerant. Refrigerant does not get used up, so low refrigerant means a leak that must be found and fixed. Topping it off without a repair only delays the next freeze. Older systems may use R-22, which our R-22 guide covers.
- A dirty evaporator coil. Built-up grime insulates the coil and blocks airflow.
- A failing blower motor that is not moving enough air.
- Duct problems such as collapsed or disconnected ducts. See our duct and airflow page.
If the ice returns within a day or two of thawing and a new filter, stop running the system and get it inspected. Running a frozen AC repeatedly can damage the compressor, the most expensive part in the system.
If your AC keeps icing up, we connect Treasure Coast homeowners with independent, licensed and insured contractors for AC repair. Use the quick form or call (772) 266-5463.
Trade Winds Air is a referral service, not a contractor. Cost figures above are general published ranges for educational purposes; every real number comes from the licensed, insured contractor who inspects your system.