Best Air Conditioners 2026

Error: E1 / F1 (Indoor Coil Sensor Failure)

The indoor evaporator coil temperature sensor is reading out of range. The AC may short-cycle or fail to regulate cooling properly. The thermistor sensor typically needs replacement by a technician.

Error: E2 / F2 (Outdoor Coil Sensor Failure)

The outdoor condenser coil temperature sensor has failed. The unit may not properly manage defrost cycles or condenser fan operation. Professional diagnosis and sensor replacement are needed.

Error: E4 / CH (Compressor Overload)

The compressor has shut down due to excessive current draw or overheating. This is a serious fault that may indicate compressor failure, low refrigerant, or electrical problems. Professional HVAC service is required.

Error: E5 / FL (Low Refrigerant)

The system has detected low refrigerant pressure, indicating a leak in the sealed refrigerant system. The AC will underperform or stop cooling entirely. A licensed HVAC technician must locate and repair the leak, then recharge the system.

Error: P1 / CF (Dirty Filter Alert)

The air filter usage timer has expired, indicating the filter needs cleaning or replacement. A dirty filter restricts airflow, reduces efficiency, and can cause the evaporator coil to freeze. Clean or replace the filter and reset the indicator.