Machine will not start; display shows F1 shortly after power-on

Safety first: Unplug the coffee machine or switch off the circuit breaker before opening any panels. Do not work on live electronics.

Basic checks:

• Disconnect the machine from power for at least 5–10 minutes to allow the control electronics to fully discharge, then reconnect and test.
• Verify the wall outlet is supplying stable voltage (use another appliance or a multimeter).
• Remove the water tank, drip tray, and waste container, then reinsert them firmly to ensure all safety switches are engaged.

Inspection:

• Remove the top cover (on built-in models, pull the unit out of the cabinet first). Look for obvious damage on the main control board: burnt spots, bulging capacitors, or a burnt smell.
• Check all wiring harness connectors to the control board (power input, display module, sensors, pumps) for loose or oxidized contacts. Reseat each connector.

When to stop:

• If F1 returns immediately after reset and no loose connections are found, the main control electronics are likely defective.
• Because this involves mains voltage and complex electronics, replacement should be done by a qualified technician. Order the exact Miele control module by model and serial number.