Microwave display shows E04 and unit will not start; interior light and fan do not come on.
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
Safety first: Unplug the microwave before removing any panels. Do not bypass fuses or safety devices.
Step-by-step:
- 1. Check the wall outlet: Plug another appliance into the same outlet to confirm power is present. Reset any tripped breaker.
- 2. Power reset: Unplug the microwave for 5–10 minutes, then plug back in. If E04 reappears immediately, an internal fault is likely.
- 3. Inspect the power cord: Look for cuts, burns, or crushed sections. Do not use the unit if the cord is damaged.
- 4. Access the internal fuse (experienced DIYers): Remove the outer cabinet. Locate the line fuse near the power cord entry or noise filter board. If the glass fuse is visibly blown (broken filament or blackened), it indicates a short or surge.
- 5. Check for obvious shorts: Inspect the noise filter board and wiring harness for burn marks, melted insulation, or loose connectors. Do not replace the fuse until the cause of the short is identified.
- 6. Replace the fuse with identical rating: If no other damage is found, replace the fuse with the exact same type and rating specified by MasterChef. Never upsize the fuse.
When to stop: If the new fuse blows immediately or E04 persists, the main control board's power supply or another component is shorted. Further diagnosis should be done by a technician.