Refrigerator shows E4 and may stop cooling periodically or show heavy frost on the evaporator

Safety: Disconnect power before accessing the evaporator, heater, or control board. The defrost heater operates at mains voltage.

Steps to troubleshoot E4:

• 1. Inspect for frost buildup: Remove freezer drawers and rear panel. If the evaporator is encased in solid ice, the defrost system is likely not working.
• 2. Visual check of heater and wiring: Look for burnt spots on the heater, broken wires, or loose connectors. The heater is usually a metal or glass tube at the base or woven through the evaporator.
• 3. Test heater continuity: With the unit unplugged, disconnect the heater leads and measure resistance. A typical heater will show a finite resistance (e.g., 50–300 Ω). Infinite resistance indicates an open heater that must be replaced.
• 4. Check defrost thermostat/thermal fuse: If present, test continuity through the thermostat or fuse when it is cold (it should be closed). An open thermostat/fuse will prevent heater operation.
• 5. Examine wiring harness: Trace the defrost circuit wiring from the heater to the control board. Repair any damaged or corroded connectors.
• 6. Control board diagnosis: If heater and thermostat test good, the control board may not be energizing the heater. This requires board-level diagnosis or replacement by a professional.

Warning: Do not bypass safety thermostats or fuses. Doing so can create a fire hazard. If unsure, call a qualified technician.