Cause

The E4 Error is not actually an error code but indicates that the air conditioner has entered defrost mode. This happens when the pipe thermistor located on the evaporator coils senses that the coil temperature is at or below 35.6 degrees ºF. When the coil temperature reaches 46.4 ºF or higher the unit will resume normal cooling operation. When the coil temperature reaches 46.4 ºF or higher the unit will resume normal cooling operation.