Ice on the AC line or coil: causes and what to check
Ice forms when the indoor coil gets too cold, and the most common reason is that not enough warm air is moving across it.
Before you start: Turn cooling off at the thermostat and set the fan to on so the ice melts. Running the AC while it is frozen can damage the compressor. Put towels down for the meltwater.
What to check first
The air filter
A clogged filter is the most common cause. Replace it.
Vents and return grilles
Open any closed vents, and move furniture and rugs off the return grilles.
Airflow at the vents
With the fan on, you should feel steady airflow. Weak airflow with a clean filter can mean a dirty blower or a failing blower motor.
The weather
Running the AC on a cool night, roughly below 60°F outside, can freeze the coil.
Refrigerant
If airflow is good and the coil freezes again, the system may be low on refrigerant from a leak. That needs a licensed HVAC technician, not a store-bought kit.
Get the list for your store
Ask Danny turns this job into a one-trip parts list for Home Depot and Lowe's, with aisle numbers and price estimates. Free, and no account needed.
Build my parts listParts you may need
- HVAC air filterThe size is printed on the frame of the old filter. Replace return grille filters too, if you have them.
- Foam AC coil cleanerOnly if you can reach a visibly dirty coil through an access panel, with the power off.
Tools
- Flashlight
- Towels or a wet/dry vacuum for the meltwater
Call a licensed pro if
- It freezes again after a new filter and open vents
- The outdoor unit buzzes, or its fan is not spinning
- You hear hissing or see oily residue at the refrigerant lines
General guidance, not professional advice. Parts differ by brand and model, so check yours before buying. Aisle numbers and prices in the app are estimates. How Ask Danny uses AI. Updated September 16, 2026.