Unit shows E4 and stops, often after running for some time; may be associated with defrost or overheat protection.

Safety first: Turn off and unplug the air conditioner before cleaning or opening panels.

• Step 1 – Clean filters: Remove and wash the air filters with mild soap and water. Let them dry completely before reinstalling.
• Step 2 – Inspect evaporator coil: With the front cover removed, check the evaporator fins for dust buildup or ice. Clean gently with a soft brush or vacuum with a brush attachment.
• Step 3 – Check indoor fan operation: Restore power and run the unit with the cover on but filters removed. Confirm that the indoor fan starts promptly and runs at all speeds. If the fan is slow or stalls, the fan motor or capacitor may be failing.
• Step 4 – Ensure vents are clear: Make sure supply and return vents are not blocked by curtains, furniture, or walls. For portable units, verify the exhaust hose is not kinked.
• Step 5 – Sensor check: If E4 recurs quickly, inspect the evaporator sensor as in the E2 procedure; a misreading sensor can falsely trigger overheat/defrost errors.
• Step 6 – PCB diagnosis: If airflow and sensors are good but E4 persists, the main PCB may be misinterpreting sensor data and should be evaluated or replaced by a technician.