Ice on your AC system is never normal during operation. Frozen coils prevent cooling and can damage the compressor if the system continues running. Here is what causes freezing and how to address it.
Signs of Frozen Coils
- AC blowing warm air
- Reduced or no airflow from vents
- Ice visible on refrigerant lines outside
- Water leaking around indoor unit when ice melts
- Hissing sound from the indoor unit
Common Causes
Restricted airflow is the most common cause. When air cannot flow freely over the evaporator coil, the coil gets too cold and moisture freezes on it.
- Dirty air filter (most common)
- Blocked return vents
- Closed supply registers
- Dirty evaporator coil
- Blower motor problems
Low refrigerant causes pressure and temperature to drop below normal, freezing the coil even with adequate airflow. Refrigerant leaks must be repaired professionally.
Low outdoor temperatures can cause freezing when running AC in cool weather. Most systems should not run AC when outdoor temps are below 60F.
What to Do
1. Turn off the AC but leave the fan running. This allows warm air to thaw the ice. Do not attempt to chip away ice.
2. Check the filter and replace if dirty.
3. Check vents and returns to ensure none are blocked.
4. Wait for complete thawing. This may take several hours. Place towels around the indoor unit to catch water.
5. Restart cautiously. Once thawed, run the system and monitor for freezing. If ice returns, turn off and call for service.
Preventing Future Freezing
- Change filters monthly during cooling season
- Keep all vents open
- Schedule annual maintenance
- Address airflow problems promptly
- Do not run AC in cool weather
When It Is More Serious
Recurring freezing despite clean filters indicates problems requiring professional attention. Low refrigerant, blower motor issues, or evaporator coil problems need proper diagnosis.
Running a frozen system damages the compressor. The compressor is the most expensive component and can cost thousands to replace. Prompt attention to freezing issues prevents costly damage.