Summit freezer shows E4 and may not defrost properly, leading to ice buildup on the evaporator.

Warning: Always disconnect power before working inside the freezer. Evaporator fins and sheet metal edges are sharp.

Steps to address E4:

• Unplug the freezer and remove the interior rear panel to access the evaporator.
• Locate the defrost probe: This is often a small sensor clipped to the evaporator tubing or mounted near the defrost heater, separate from the main evaporator thermistor.
• Check attachment: Ensure the probe is firmly clipped to the tubing or bracket as designed. A loose or dangling probe can read incorrect temperatures and trigger E4.
• Inspect wiring: Look for cracked insulation, pinched wires, or signs of moisture intrusion at the connector. Reseat the connector to the harness and to the control board if accessible.
• Test the probe: With a multimeter, measure resistance at room temperature and compare to specifications (NTC-type sensor). If the reading is open, shorted, or far from expected, the probe is faulty.
• Replace the defrost probe: Install a Summit-compatible defrost sensor. Clip it securely in the original location to ensure accurate sensing during defrost cycles. Route wires away from the fan and heater.
• Reassemble and power up: Reinstall the panel, plug the unit back in, and allow the control to cycle. The E4 code should clear once the control detects valid readings.

Note: Persistent E4 with a known-good probe suggests a control board sensing circuit failure, which typically requires professional replacement.