Microwave display shows E04 and the unit will not start; sometimes accompanied by a loud hum or tripping the household breaker.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Danger: This fault involves the high-voltage system. Unplug the microwave immediately and do not attempt to run it again until inspected. High-voltage shorts can cause fire or severe electric shock.
- User-level actions:
- Disconnect from mains and leave unplugged.
- Check that the wall outlet and circuit are not overloaded with other high-power appliances.
- Technician-level checks (summary):
- Discharge the high-voltage capacitor safely.
- Test the HV capacitor for shorts or loss of capacitance.
- Test the HV diode for short or open circuit.
- Check magnetron resistance between terminals and to chassis for shorts.
- Inspect the HV transformer for burnt smell or visible damage.
Because of the complexity and danger, this repair should be carried out by a qualified appliance technician familiar with Bush microwave high-voltage systems.
Repair Difficulty
Required Part
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