Ice maker shows E4 and shuts down, compressor does not run

Safety: Disconnect power before accessing internal components. Avoid touching the compressor or condenser coils when hot.

Diagnostic steps:

• Power cycle: Turn OFF, unplug for 5–10 minutes, then plug back in and restart. If E4 returns immediately, proceed with inspection.
• Locate the thermistor: Remove the rear or side panel to access the evaporator area. The thermistor is usually a small probe clipped to the evaporator plate or tubing with two wires leading to the control board.
• Check attachment: Ensure the thermistor is firmly clipped to the evaporator surface and not dangling. Poor contact can cause incorrect readings.
• Inspect wiring and connector: Follow the thermistor wires to the control board. Confirm the connector is tight and free of corrosion or moisture.
• Basic resistance check (for advanced DIYers): With the unit unplugged, disconnect the thermistor from the board and measure resistance with a multimeter. Compare to the service chart if available (typically 5–50 kΩ depending on temperature). An open (infinite) or 0 Ω reading indicates a bad sensor.

Next steps: If wiring is intact and resistance is out of spec, replace the evaporator thermistor. If a known-good thermistor still triggers E4, the control board temperature circuit is likely defective and should be replaced by a technician.