RCA freezer displays E4 and may show heavy frost on the evaporator or warm cabinet temperature.

Safety first: Unplug the freezer before accessing the evaporator or control board. The defrost heater and wiring can be live and hot during operation.

Steps to troubleshoot E4:

• 1. Inspect for frost: Remove food and shelves, then the rear interior panel. If the evaporator is encased in solid ice, the defrost system is likely not working.
• 2. Locate defrost thermostat and heater: The defrost thermostat (bi-metal) is clipped to the evaporator tubing; the heater is usually a glass or metal element at the bottom or woven through the coil.
• 3. Test defrost thermostat: With the unit unplugged and the thermostat still cold (below freezing), disconnect its wires and check continuity. It should read closed (0 Ω). If open when cold, replace it.
• 4. Test defrost heater: Disconnect heater leads and measure resistance. A typical heater will show some resistance (e.g., 20–150 Ω). An open circuit (OL) indicates a failed heater that must be replaced.
• 5. Check wiring: Inspect harnesses from the heater and thermostat back to the control board for burns, breaks, or loose connectors. Repair or replace damaged wiring.
• 6. Manually defrost: Fully defrost the evaporator with towels and a hair dryer on low (do not overheat plastic). Ensure all ice is removed before reassembly.
• 7. Reassemble and test: Replace any failed components with RCA-compatible parts, reinstall the evaporator cover, restore power, and monitor for 24–48 hours to confirm normal frost pattern and no return of E4.

Note: If heater and thermostat test good, the main control board's defrost circuit may be defective and should be replaced by a qualified technician.