Symptoms
- Visible ice on the outdoor unit's coil or refrigerant lines during summer cooling season
- Reduced or no cooling performance
- May be paired with ice on the indoor coil as well
Likely causes
- CommonLow refrigerant from a leakReduced refrigerant pressure causes the coil to run too cold, leading to ice even in warm weather.
- CommonRestricted airflow at the indoor coil (dirty filter or blocked vents)Poor airflow indoors can cause ice to form and extend all the way out to the outdoor lines.
- PossibleDirty outdoor condenser coilA coil that can't release heat properly can throw off the refrigerant cycle's balance.
- PossibleFailing blower motor reducing airflowWeak airflow from the indoor fan has the same icing effect as a dirty filter.
What to do
- Turn the system to Fan Only (not Off) to help everything thaw without further stressing the compressor.
- Replace the indoor air filter and confirm all vents are open.
- Clean the outdoor condenser coil of dirt and debris once accessible.
- Let the system fully thaw, which can take several hours, before restarting cooling mode.
- Watch for ice returning within a few hours of restarting, which strongly suggests low refrigerant.
- Call an HVAC technician for a refrigerant leak check if ice keeps returning after airflow fixes.
Tools and parts
- Garden hose
AC air filterSearch: “central air filter size replacement”
When to call a pro
Call an HVAC technician for a refrigerant leak check if the outdoor unit ices up in warm weather even after clearing filters and vents.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.