Microwave display shows E4 and unit will not start; sometimes appears after a power surge or lightning storm.

Safety: Unplug the microwave before opening the cabinet. Avoid touching the high-voltage section.

Basic reset:

• Unplug the microwave for at least 5 minutes to allow the control board to fully discharge.
• Plug back in and check if E4 clears. If it returns immediately, proceed with inspection.

Inspection steps:

• Remove the outer cabinet to access the main control board (usually behind the control panel).
• Inspect the board for burnt components, bulging capacitors, or darkened areas.
• Check all wiring harnesses to the control board and display/keypad for secure connections; reseat any loose connectors.
• Verify the line fuse and thermal fuses are intact (if blown, determine and correct the cause before replacing).

Corrective actions:

• If the board shows obvious surge damage or burnt traces, replace the main control board with a Magic Chef-compatible PCB.
• If wiring is damaged or melted, repair or replace the harness and inspect nearby components for shorts.
• After replacement, reassemble, restore power, and test all functions (clock, cook, defrost, timer).

Note: Control board diagnosis beyond visual inspection often requires live voltage testing and schematic interpretation; if you are not comfortable with this, contact a professional.