Microwave display shows E04 and the unit will not start; sometimes accompanied by interior light flickering or fan not running.
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. Avoid touching the high-voltage section.
Step-by-step checks:
- 1. Power reset: Disconnect the microwave from mains for at least 5 minutes to allow capacitors on the control board to discharge. Plug back in and check if E04 clears.
- 2. Inspect power cord and plug: Check for damage, burns, or loose connections at the plug and where the cord enters the microwave.
- 3. Access the control panel: Remove the outer cabinet and then the control panel mounting screws. Carefully tilt the control panel forward to access the wiring harnesses.
- 4. Check harness connections: Ensure all connectors to the control PCB are fully seated and free of corrosion or burn marks. Reseat each connector one at a time.
- 5. Inspect the PCB: Look for burnt components, cracked solder joints, or bulging electrolytic capacitors on the control board.
- 6. Test keypad (if separate from PCB): If your Grundig model uses a separate membrane keypad, disconnect its ribbon cable and see if E04 changes or clears when powered on (do not run the microwave with panels removed). A shorted keypad can pull down the low-voltage supply.
If visual inspection reveals PCB damage or E04 persists after reseating connectors and isolating the keypad, the control board will likely need replacement by a professional.