Danby refrigerator displays E4 and may not defrost; frost accumulates on the evaporator and back wall.

Safety: Unplug the refrigerator before testing the heater or thermostat. Avoid working on live circuits unless you are trained and using proper tools.

Steps to diagnose E4:

• Access the evaporator: Remove freezer contents and the rear interior panel to expose the evaporator coil and defrost components.
• Locate the defrost heater: On Danby units, it is typically a glass-encased or metal tube heater mounted at the bottom or woven through the evaporator.
• Test the heater: Disconnect heater leads and measure resistance with a multimeter. A typical heater will show a finite resistance (e.g., 20–150 Ω). If it reads open (OL), replace the heater.
• Check the defrost thermostat/thermal fuse: The thermostat is usually clipped to the evaporator tubing. At freezing temperatures, it should read closed (near 0 Ω). If it is open when cold, replace it.
• Inspect wiring and connectors: Look for burnt connectors, brittle wires, or loose plugs between the heater, thermostat, and main control board. Repair or replace as needed.
• Control board check: If heater and thermostat test good and wiring is intact, the main control board defrost relay or logic may be faulty. Board replacement is recommended to be done by a qualified technician.