Whirlpool undercounter ice maker displays E1 and stops making ice

Safety first: Unplug the ice maker or switch off the circuit breaker before removing any panels.

• Access the evaporator thermistor: Remove the front kick plate and lower access panel. On many Whirlpool undercounter units, the evaporator thermistor is clipped to the evaporator plate or tubing in the ice-making compartment.
• Inspect the sensor and wiring: Look for broken wires, corrosion at the connector, or a thermistor that has fallen off the evaporator surface. Reseat the connector firmly.
• Test the thermistor: With a multimeter set to resistance (ohms), disconnect the thermistor and measure its resistance at room temperature. Compare to Whirlpool’s service chart (commonly ~10kΩ at 77°F/25°C). If reading is open (OL), 0Ω, or far out of spec, the thermistor is bad.
• Check harness to control board: Follow the harness from the thermistor to the main control board. Look for pinched or rubbed-through insulation. Repair any damaged wiring and ensure connectors are fully seated on the board.
• Reset and test: Restore power and clear the error (if the model has a service mode or power-reset procedure). Run a test cycle and verify the E1 code does not return.
• If the code persists with a good thermistor: The thermistor input circuit on the main control board may be defective and the board will need replacement.