Safety first: Unplug the cooler. Be cautious of sharp metal edges and ice buildup.

Access evaporator: Empty the affected compartment. Remove the rear interior panel (evaporator cover) by taking out the screws and gently pulling it forward.
Locate sensor: Find the small probe clipped to or near the evaporator coil. Check that it is firmly attached and not encased in heavy ice.
Inspect wiring: Look for nicks, cuts, or broken insulation where the sensor wires pass through the foam or near the evaporator fan.
Defrost if iced: If the evaporator is heavily iced, allow it to fully defrost (leave unplugged with doors open and towels in place) before further inspection.
Replace sensor: If the sensor is damaged or E4 persists, replace the evaporator temperature sensor with the correct NEEDONE part. Clip it securely to the coil as originally installed.
Reassemble and test: Reinstall the evaporator cover, restore power, and confirm that the E4 code clears and cooling resumes normally.

Display shows E4 and the unit may run continuously or not cool properly.

Possible Causes