Freezer shows E3; defrost cycle may not run correctly, frost buildup on evaporator

Safety first: Unplug the freezer before removing the evaporator cover or working near wiring.

• Access the evaporator: Remove baskets and shelves, then remove the rear interior panel to expose the evaporator coil.
• Locate defrost sensor: The defrost thermistor or bi-metal sensor is clipped to the evaporator tubing or near the top of the coil. It will have two wires leading to it.
• Check for heavy frost: If the coil is completely encased in ice, manually defrost with a hair dryer on low, keeping the dryer away from plastic parts and wiring. Do not chip ice with sharp tools.
• Test the sensor: Disconnect the sensor and measure resistance (for thermistor) or continuity (for bi-metal) at a known temperature. Compare to the tech sheet. Replace if open, shorted, or out of range.
• Inspect wiring: Check the harness from the sensor to the control board for breaks or corrosion. Repair or replace as needed.
• Replace control board: If the sensor and wiring are good but E3 remains, replace the main control board.