Air Conditioning troubleshooting
AC Freezing Up? Why There's Ice on Your Unit
Ice on an air conditioner means the coil got too cold, almost always from airflow or refrigerant. Running it frozen can damage the compressor.
Common causes
Dirty filter or blocked airflow
You can checkLow airflow over the coil drops its temperature below freezing and ice forms.
Low refrigerant (leak)
Pro repairA low charge makes the coil too cold and ice over — it needs leak repair and recharge.
Dirty evaporator coil
Pro repairA grimy indoor coil insulates and freezes; it needs professional cleaning.
Failed blower fan
Pro repairA weak or stopped indoor fan can't move enough air over the coil.
What you can check yourself
- Turn the AC OFF (fan ON) to let the ice fully thaw — don't run it frozen.
- Replace the air filter.
- Open all vents and make sure return air isn't blocked.
- Once thawed, if it freezes again quickly, stop and call.
When to call a pro
Repeated freezing after a filter change means low refrigerant, a dirty coil, or a blower problem — all technician repairs.
Most air conditioner repairs run $150–$1,200 — see our repair cost guide.
Other air conditioning problems
FAQ
AC freezing up — questions
Ice on an air conditioner means the coil got too cold, almost always from airflow or refrigerant. Running it frozen can damage the compressor. The most common causes are dirty filter or blocked airflow, low refrigerant (leak), dirty evaporator coil.
You can safely check a few things first: Turn the AC OFF (fan ON) to let the ice fully thaw — don't run it frozen. Replace the air filter. Open all vents and make sure return air isn't blocked. Repeated freezing after a filter change means low refrigerant, a dirty coil, or a blower problem — all technician repairs.
Most air conditioner repairs run $150–$1,200 in the San Francisco Bay Area, parts and labor — you get a flat-rate quote before any work begins. See our repair cost guide for details.
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