Microwave displays E18 and emits a continuous or repeated beeping; may indicate internal communication error between boards (for combo models).

Safety first: Unplug the microwave before accessing internal boards.

Step-by-step checks:

• 1. Power reset: Unplug for 10 minutes, then plug back in to clear transient communication faults.
• 2. Inspect harnesses: Remove the cover and locate any multi-wire harnesses connecting separate boards (e.g., main control to inverter or display board). Reseat each connector firmly.
• 3. Check for corrosion: Look for moisture or corrosion on connectors and boards, especially in humid kitchen environments.
• 4. If a board was recently replaced: Ensure the replacement is the correct Paderno part number and firmware revision for your model.
• 5. Persistent E18: Usually indicates a failing board; professional diagnosis and board replacement are recommended.