Symptoms
- Frost or ice visible on the thin copper line near the outdoor or indoor unit
- Reduced cooling performance
- Water dripping as the ice melts during off cycles
Likely causes
- CommonLow refrigerant chargeLow refrigerant drops line pressure and temperature enough to freeze condensation on the line.
- CommonRestricted airflow at the indoor coilA dirty filter or blocked vents can cause the same icing pattern seen on refrigerant lines.
- PossibleDirty outdoor condenser coilReduced heat rejection outside can throw off the whole refrigerant cycle's balance.
- Less commonFailing metering device (TXV or orifice)A malfunctioning metering device can cause abnormal refrigerant flow and icing.
What to do
- Turn the system off, but run the fan alone to help the ice melt without further damaging the compressor.
- Replace the air filter and confirm all vents are open.
- Clean the outdoor condenser coil of dirt, leaves, or grass clippings with the power off.
- Let everything thaw fully before restarting, which may take a few hours.
- Watch for ice returning shortly after restarting, which points to refrigerant level as the likely culprit.
- Call a technician for a refrigerant check and leak test if icing returns despite good airflow.
Tools and parts
- Garden hose
When to call a pro
Call an HVAC technician for a refrigerant charge check and leak detection if ice keeps forming on the lines after airflow fixes.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.