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Cooling

Why Is My AC Freezing? Causes and Next Steps

Finding ice on your air conditioner is alarming — especially in the middle of a hot summer. A frozen AC can't cool your home effectively, and if you keep running it, you risk damaging the compressor, which is the most expensive component in the system.

Here's what causes AC freezing and what to do about it.

Restricted airflow is the most common cause. When airflow over the evaporator coil drops below a certain level, the coil gets too cold and ice forms. The most frequent culprit is a dirty air filter. Check and replace the filter first. Also make sure all supply and return vents are open and unobstructed.

Low refrigerant is another common cause. Refrigerant absorbs heat from the air inside your home. When the level is low — usually due to a leak — the pressure in the system drops, the coil gets too cold, and ice forms. Low refrigerant is not something you can fix yourself; it requires a licensed technician to find the leak and recharge the system.

Dirty evaporator coils can also cause freezing. Over time, dust and debris build up on the coils, insulating them and reducing heat transfer. This can cause the coil temperature to drop below freezing. Coil cleaning is part of a standard annual maintenance visit.

Running the AC when it's too cold outside can cause freezing. Most central AC systems aren't designed to operate when outdoor temperatures drop below about 60°F. If you're running the AC on a cool night, the system may freeze.

What to do right now: Turn the AC off and switch the fan to 'on' (not 'auto') to circulate air over the coil and help it thaw. This typically takes 1 to 3 hours. Do not run the AC while it's frozen — you risk compressor damage. Once it's thawed, check the filter and restart the system. If it freezes again, call a technician.

West Coast Air Conditioning diagnoses and repairs frozen AC systems throughout Calaveras and San Joaquin County. Call (209) 598-8889.

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