Display shows E4 and cabinet temperature fluctuates widely or unit shuts down unexpectedly

Safety: Disconnect power before accessing the evaporator area. Edges of metal panels and coils can be sharp.

Procedure:

• Defrost first: If there is heavy ice buildup, leave the door open and unplug the unit for several hours to melt ice. Place towels to catch water.
• Access evaporator: Remove interior rear panel inside the cooled compartment to expose the evaporator coil and fan assembly.
• Locate sensor: Find the small NTC probe clipped or strapped to the evaporator tubing. Ensure it is firmly attached and not hanging loose.
• Inspect for damage: Look for crushed wires, cracked sensor body, or corrosion where the sensor enters its sheath.
• Check wiring to board: Trace the sensor harness through the cabinet to the control board. Verify no pinched sections and that the connector is fully seated.
• Test sensor: With the unit unplugged, disconnect the sensor and measure resistance. Compare to other cabinet sensors. Replace if readings are out of range or intermittent when gently flexing the wire.
• Replace sensor: Install a new Transtherm evaporator NTC sensor, clipping it securely to the coil in the same position to ensure accurate defrost control.
• Reassemble and test: Refit the interior panel, restore power, and monitor operation. The E4 code should clear once the control detects a valid sensor signal.

Warning: Do not use sharp tools to remove ice from the evaporator; you can puncture the refrigerant tubing and render the cabinet non-repairable.