Microwave displays E10 and refuses to start; sometimes accompanied by a relay click.

Safety: Unplug the microwave. High-voltage and mains circuits are present on the control board.

User-level:

• 1. Power reset: Unplug for 5 minutes, then reconnect and test. If E10 returns immediately, an internal control fault is likely.
• 2. Observe behavior: Listen for repeated clicking when pressing START. Multiple rapid clicks can indicate a relay or control issue.

Technician-level:

• Remove the cabinet and inspect the control board for burnt relay contacts, discoloration, or cracked solder joints.
• Test the relay coil and contacts with a multimeter.
• Check connected loads (transformer, inverter, fan) for shorts that could cause relay failure.

Recommendation: Control board repair or replacement should be performed by a qualified technician. In many cases, the entire Sharp control PCB is replaced as a unit.