GE air conditioner displays E4 and may stop cooling or enter a protection mode

Safety: Unplug the unit before servicing. Allow any ice on the coils to melt to avoid water on electrical parts.

Steps:

• Visual inspection: Remove the front cover and inspect the evaporator coil for heavy frost or ice buildup. If iced over, leave the unit unplugged until fully defrosted.
• Locate defrost/frost sensor: On many GE models, the same evaporator thermistor is used for frost protection. It will be clipped to the evaporator coil tubing.
• Check attachment: Ensure the sensor is firmly attached to the coil and not hanging loose. Re-secure with the original clip or foil tape.
• Inspect wiring: Look for damaged or pinched wires between the sensor and control board. Repair or replace the harness if needed.
• Test sensor: Measure resistance and compare to GE specifications. Replace the sensor if readings are out of range.
• Check airflow: Dirty filters or blocked coils can cause frost and trigger E4. Clean the air filter and gently brush or vacuum dust from the evaporator fins.
• Control board: If sensor and airflow are correct but E4 persists, the main control board may be misreading the sensor and should be replaced.

Note: Persistent icing can also indicate low refrigerant or a failing expansion device, which requires professional service.