Microwave shows E17 and stops immediately when START is pressed; sometimes accompanied by a relay click.

Safety first: Unplug the microwave. Do not repeatedly attempt to start the unit if it stops instantly with an error.

Step-by-step checks:

• 1. Listen for relay: When pressing START, listen for a click from inside. A rapid click followed by shutdown suggests relay or load issues.
• 2. Visual inspection: Remove the cover and inspect the control board relays for discoloration or cracking.
• 3. Check for obvious shorts: Look for burnt wires or components in the high-voltage and heater circuits (without touching them).
• 4. Technician testing: Relay testing and replacement typically require desoldering and should be done by a professional. For most users, replacing the entire control board is the practical solution.