Display shows E4 and the compressor or cooling system may not run correctly; unit may shut down prematurely.

Warning: Unplug the cooler before accessing the evaporator or control board. Do not attempt to test live circuits unless you are trained and using proper tools.

• Check for heavy frost: Remove interior shelves and the rear panel inside the cabinet. If the evaporator coil is encased in solid ice, the defrost system is likely not working.
• Manual defrost: With the unit unplugged, allow the ice to melt naturally or use bowls of warm water inside the cabinet. Do not use sharp tools or hair dryers, as they can damage plastic and seals.
• Locate defrost sensor: Look for a small sensor clipped to the evaporator tubing or attached near the top of the coil. Inspect for broken wires or a loose clip.
• Inspect defrost heater (if visible): Some Phiestina models have a heater element at the base of the evaporator. Check for obvious breaks or burn marks.
• Check wiring and connectors: Follow the sensor and heater wires to the harness and main control board. Ensure all plugs are fully seated and free of corrosion.
• Replace faulty components: If the defrost sensor is cracked or tests open/shorted with a multimeter, replace it with a "Phiestina defrost sensor". If the heater is visibly broken or tests open, replace the "Evaporator defrost heater".
• Reassemble and test: Reinstall the interior panel, plug the unit back in, and monitor for the E4 code. The cooler should now defrost automatically and maintain temperature without heavy ice buildup.