Unit displays E4 and may stop cooling; sometimes accompanied by coil icing or frequent compressor cycling.

Safety: Turn the unit off and unplug it. Allow any ice on the coils to melt before working inside the cabinet.

Steps to address E4:

• Thaw the unit: Leave the unit unplugged with the front cover removed for several hours until all ice has melted. Place towels to catch water.
• Clean air filter: Remove and wash the filter with mild soap and water. Let it dry completely before reinstalling.
• Inspect evaporator coil: Check for dust, lint, or debris blocking airflow. Use a soft brush or vacuum with a brush attachment to gently clean the fins.
• Check evaporator sensor placement: Ensure the evaporator thermistor is properly clipped to the coil and not buried in ice or hanging loose. Reposition if necessary.
• Verify fan operation: With the unit reassembled and powered, run in fan-only mode. Confirm the indoor blower runs smoothly at all speeds. A weak or non-running fan can cause icing and E4.
• Sensor/board check: If E4 returns quickly after cleaning and thawing, test the evaporator sensor as described for E2. Replace the evaporator temperature sensor if readings are abnormal. Persistent E4 with a good sensor and clean coil may indicate a main control board issue or low refrigerant, which requires a licensed technician.