Unit shuts down and displays E4, often after running for some time; may be accompanied by ice on the evaporator or very low airflow.

Safety first: Turn the unit off and unplug it before removing covers. Do not attempt to open the sealed refrigeration system yourself.

Steps to address E4:

• 1. Thaw the unit: Turn the air conditioner off and let it sit with the fan-only mode (if available) for 1–2 hours to melt any ice on the evaporator coil.
• 2. Clean the air filter: Remove the front grille and filter. Wash the filter with mild soap and warm water, rinse thoroughly, and let it dry completely before reinstalling.
• 3. Check indoor airflow: Ensure supply and return vents are not blocked by furniture, curtains, or covers. Verify that the blower fan is running smoothly and at normal speed.
• 4. Inspect evaporator sensor: With power disconnected, remove the front cover and confirm the evaporator thermistor is firmly attached to the coil and not dangling in free air.
• 5. Coil cleanliness: If the evaporator coil is clogged with dust, gently vacuum with a soft brush or use a coil cleaner designed for evaporator coils. Avoid bending fins.
• 6. Restart and test: Restore power and run the unit. If E4 returns quickly and the coil ices up again, there may be a refrigerant or blower motor issue.
• 7. Call a professional: Low refrigerant charge, a weak blower motor, or a faulty control board require an EPA-certified technician to diagnose and repair.