Microwave displays E4 and stops heating mid-cycle

Safety first: Unplug the microwave. Internal components can be hazardous.

• 1. Allow cooling: If the microwave has been used repeatedly, let it cool for at least 20–30 minutes with the door open, then try again. Over-temperature can trigger E4 on some Russell Hobbs models.
• 2. Check ventilation and installation: Ensure the unit is not built into a tight space without proper airflow. Clear any obstructions from the vents.
• 3. Inspect for heavy grease buildup: Excess grease on the cavity ceiling and walls can trap heat. Clean thoroughly with a non-abrasive cleaner and dry.
• 4. Internal thermistor check (advanced): Remove the outer cover with the unit unplugged. Locate the cavity thermistor (often clipped to the top or side of the cavity). Check that it is firmly attached and that its wires are intact and connected to the control board.
• 5. Test thermistor: Using a multimeter, measure resistance at room temperature and compare with service data if available. A reading of near 0 Ω (short) or infinite (open) indicates a failed sensor that must be replaced.
• 6. If E4 remains: The control PCB may be misreading the sensor. Professional diagnosis is recommended.