Frozen AC Coils

Priority

Ice formation on evaporator coil or refrigerant lines preventing proper cooling.

Frozen coils prevent cooling and can damage compressors. Ice forms when refrigerant temperature drops below normal due to insufficient airflow or low refrigerant charge. Turn off the system to let ice melt before attempting diagnosis. The most common cause is dirty filters, which is easy to fix. Refrigerant issues require professional service.

Symptoms to Look For

Ice visible on indoor coil or refrigerant lines
Water leaking when ice melts
AC blowing warm air
Reduced or no airflow from vents
System running but not cooling

Possible Causes

1Dirty air filter severely restricting airflow
2Refrigerant leak reducing system charge
3Blower motor failure or reduced speed
4Blocked evaporator coil
5Collapsed ductwork or blocked vents
6Low outdoor temperatures during operation
7Failed expansion valve or metering device

What You Can Check

Before calling for service, try these safe checks that may resolve simple issues:

Turn off AC and let ice melt
Check and replace air filter
Ensure all vents are open
Look for obvious duct damage
Check blower operation

When to Call a Professional

If freezing recurs after filter replacement and defrosting, refrigerant levels or other issues need professional diagnosis. Running a frozen system risks compressor damage.

Need HVAC service?

Call (650) 540-7205 or book online.

Prevention Tips

Change filters monthly during cooling season
Keep vents open and unobstructed
Schedule regular maintenance
Address airflow issues promptly
Do not run AC when outdoor temps are below 60F

Frequently Asked Questions

What should I do if I see ice on my AC?

Turn off the AC but leave the fan running to help melt ice. Check and replace the filter. Once defrosted, try running again. If ice returns, call for service.

Can I chip away the ice to fix the problem?

No. Forcing ice off can damage coils and fins. Let it melt naturally with the system off. Running a frozen system risks compressor damage from liquid refrigerant.

Why does low refrigerant cause freezing?

Low refrigerant reduces pressure, which lowers the evaporation temperature. The coil gets colder than designed, causing moisture in the air to freeze on it rather than drain away.

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