A frozen AC — ice on the copper refrigerant line or the indoor coil — is almost always caused by restricted airflow (a dirty filter or blocked vents) or low refrigerant. The fix has two parts: thaw it out completely by turning cooling off and the fan on, then remove whatever choked the airflow. If it freezes again after a clean filter and clear vents, the cause is refrigerant and needs a pro.
Watch how it's done
Video: Home Caprice. Shown for reference — not affiliated with GetHoustonLeads.
What you'll need
- A fresh air filter
- Towels (to catch meltwater)
- A flashlight
Recommended parts & supplies
- HVAC air filter (check your size) — a clogged filter is the top cause of freezing
- AC coil cleaner spray — for a dirty coil after thawing
- Open/adjustable vent registers — if closed vents restricted your airflow
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Step by step
- 1
Turn cooling OFF and the fan ON to thaw it
At the thermostat, set mode to OFF and the fan to ON. Running the blower with the compressor off pushes room-temperature air across the coil and melts the ice fastest. A fully frozen system can take two to four hours to thaw — don’t rush it, and never chip or scrape the ice, which can puncture the coil.
- 2
Put towels down to catch the meltwater
As the ice melts, it becomes water — often more than the drain pan expects. Lay towels around the indoor unit and check them as it thaws so you don’t end up with water damage while you wait.
- 3
Replace the air filter
While it thaws, swap in a clean filter. A clogged filter is the number-one cause of a frozen coil, because starved airflow lets the coil drop below freezing. If yours was dirty, you’ve likely already found the cause.
- 4
Open and unblock your supply vents
Walk the house and make sure supply registers are open and not blocked by furniture, rugs, or closed doors in unused rooms. Closing too many vents restricts airflow enough to freeze the coil — a surprisingly common cause in homes trying to “save energy” by shutting rooms off.
- 5
Restart and watch for re-freezing
Once every trace of ice is gone (feel the lines — they should be dry and not cold-to-frost), set the thermostat back to COOL. Let it run an hour, then check the same spots. Clear lines and cold vents mean you fixed it. Fresh frost forming again points to low refrigerant.
When to call a pro
If your AC freezes up again after a clean filter and open vents, the cause is almost certainly low refrigerant from a leak — and that requires a licensed, EPA-certified tech to find, seal, and recharge. Running a frozen or low-charge system damages the compressor, so don’t keep cycling it. Also call a pro if the coil is so iced you can’t find the source, or if the blower motor itself is failing (weak airflow even with a clean filter).
Get a free quote from a local pro
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Ice on Your AC — FAQ
Why does my AC keep freezing up?
Can I just scrape the ice off my AC coil?
How long does it take a frozen AC to thaw?
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