E4 error on display; unit may stop mid-cycle or fail to start, sometimes after a defrost or long run period.

Safety first: Disconnect power before opening the cabinet or control panel.

• Locate the ambient sensor: On many Swan ice makers, the ambient sensor is mounted near the air intake grille or on the control board housing, with two small wires.
• Check mounting: Ensure the sensor is not dangling or pressed against a hot component (like the compressor). Reposition it to its original clip or bracket.
• Inspect wiring: Look for cuts, abrasions, or melted insulation along the sensor wires. Repair or replace if damaged.
• Check connector: Confirm the sensor plug is fully seated on the control PCB and free of corrosion.
• Test operation: Reassemble, plug in, and restart. If the error reappears immediately, the sensor or board is likely faulty.

Replacing the ambient temperature sensor is usually straightforward. If a new sensor does not resolve E4, the main control board may require replacement.