Short answer
Set the thermostat to "Off" and the fan to "On" so the house air melts the ice. Replace a dirty air filter and open any closed vents. Let it thaw completely, usually a few hours, with towels under the indoor unit, and do not chip the ice. Then set it back to "Cool". If it freezes again, call a technician: low refrigerant from a leak is a job for a pro.
How to thaw a frozen AC
1Ice on the copper lines
Frost or ice on the lines by the outdoor unit, or on the indoor coil, and weak air from the vents. Running it like this strains the compressor.
Read all the steps
- Ice on the copper lines. Frost or ice on the lines by the outdoor unit, or on the indoor coil, and weak air from the vents. Running it like this strains the compressor.
- Thermostat to Off, fan to On. The outdoor unit stops and the indoor fan keeps blowing house air over the coil. That melts the ice faster than turning everything off.
- Replace a dirty air filter. A clogged filter is the most common cause. Put in a new one of the same size, and open any closed or blocked vents.
- Let it thaw all the way. It usually takes a few hours. Put towels under the indoor unit for the meltwater. Do not chip or scrape the ice.
- Back to Cool once it is dry. Set the thermostat to "Cool" again. If the ice comes back within a day or two, call a technician: it is likely low refrigerant.
- Still not fixed? Call an HVAC contractor Especially if: the ice comes back after you thaw it and replace the filter.
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Why an AC freezes
- Not enough airflow: a dirty filter, closed or blocked vents, or a dirty indoor coil.
- Low refrigerant from a leak. The coil gets too cold and the moisture in the air turns to ice.
- An indoor blower that runs slow or not at all.
- Running the AC on cool nights, which can freeze some systems.
What not to do
- Do not chip, scrape or hit the ice. You can puncture the coil or the lines.
- Do not use a heat gun, torch or hair dryer on the coil. It can damage parts, and it is electricity near water.
- Do not keep it on "Cool" while it is frozen. The ice gets worse and the compressor suffers.
- Do not add refrigerant yourself. Handling it requires certification, and low refrigerant means a leak.
When to call an HVAC technician
- The ice comes back after you thaw it and replace the filter.
- You hear hissing or bubbling, or see oily spots on the lines (signs of a refrigerant leak).
- The meltwater overflows the drain pan or stains the ceiling.
- The indoor fan does not blow, even with the fan set to "On".
Frequently asked questions
How long does it take for a frozen AC to thaw?
Usually one to a few hours with the thermostat on "Off" and the fan on "On". Heavy ice can take most of a day. Wait until the coil and the lines are dry before you set it back to "Cool".
Can I run my AC if it is frozen?
No. Running it on "Cool" while it is frozen makes the ice worse and can damage the compressor. Switch to "Off" with the fan "On" until it thaws.
Why is there ice on my AC lines?
The coil is getting too cold, usually because of poor airflow (a dirty filter or closed vents) or low refrigerant from a leak. Fix the airflow first. If it freezes again, call a technician.
Can a dirty filter make my AC freeze?
Yes, it is one of the most common causes. Less air over the coil lets it drop below freezing. Check the filter every month while you use the AC.
Should I turn off my AC if it is frozen?
Set the thermostat to "Off" and the fan to "On". The fan blows house air over the coil and melts the ice faster than shutting everything off.
Does a frozen AC mean it needs refrigerant?
Often, but not always. If a new filter and open vents do not stop the ice, have a technician check for a leak. Adding refrigerant without fixing the leak only lasts a short time.