Display shows E4; unit may shut down to protect itself, often after running for some time in cooling mode.

Safety first: Disconnect power before opening the front panel. Water and ice may be present around the coil.

Steps to address E4:

• 1. Thaw the unit: Turn the unit off and allow any ice on the evaporator coil to melt completely. Place towels under the unit to catch drips.
• 2. Clean air filter and grille: Remove and wash the air filter with mild soap and water. Ensure the front grille and air intake are not blocked by dust or objects.
• 3. Inspect evaporator coil: With the front cover removed, check for heavy dirt buildup on the coil. If dirty, gently clean with a soft brush or coil cleaner, avoiding bending fins.
• 4. Locate frost sensor: Many Insignia models use the same evaporator thermistor for frost protection. Confirm it is firmly attached to the coil in the correct location (usually mid-coil). Reattach if loose.
• 5. Check fan operation: Power the unit briefly (with covers in place) and verify the indoor fan runs at all selected speeds. Poor airflow can cause freezing and trigger E4.
• 6. Replace sensor if faulty: If the sensor tests open/shorted or E4 appears immediately on startup, replace the evaporator/frost sensor with the correct Insignia part.
• 7. Persistent E4: If airflow is good, coil is clean, and sensor is new, the main PCB may be misinterpreting sensor data. Board replacement or professional diagnosis is recommended.