Unit powers on but quickly shows E4; compressor may not run or shuts off quickly.

Safety first: Unplug the ice maker before removing any panels. Avoid touching sharp metal edges around the evaporator.

• Reset the unit: Unplug for 10–15 minutes, then plug back in and restart. If E4 returns immediately, proceed with inspection.
• Locate the evaporator sensor: Open the lid and find the metal evaporator fingers or plate where ice forms. The thermistor is usually clipped or taped to the side or underside of this assembly, with two thin wires leading to the control board.
• Check sensor placement: Ensure the thermistor is firmly attached to the evaporator surface and not hanging loose. Re-clip or re-tape it if necessary using aluminum tape or the original clip.
• Inspect wiring: Follow the sensor wires back to the control board. Look for cuts, pinches, or corrosion. Reseat the connector on the PCB.
• Test the thermistor (advanced): With the unit unplugged, disconnect the thermistor and measure resistance with a multimeter. At room temperature, it should read within the expected range (often 5–20 kΩ). If it reads open or shorted, it is defective.
• Replace the sensor: Order an Igloo-compatible evaporator thermistor. Remove the old sensor, attach the new one firmly to the evaporator in the same location, and reconnect to the board.
• Control board check: If a new sensor does not clear E4 and wiring is intact, the main control board may be faulty and require replacement.