Display shows F04, oven may not heat correctly or may overshoot temperature.

Safety first: Isolate the oven from mains power before removing panels.

Step-by-step checks:

• Verify correct sensor part: Compare the installed NTC sensor part number with the V-ZUG spare parts list for your exact model. Using a non-original or wrong-value sensor can trigger F04.
• Inspect connector seating: Remove and reinsert the sensor plug on the main PCB several times to clean contacts. Ensure it is fully latched.
• Check resistance vs. temperature: Measure sensor resistance at room temperature and, if possible, at a known higher temperature (e.g., 100°C in boiling water, with sensor removed from oven). Compare with V-ZUG service chart. Large deviations indicate a faulty sensor.
• Perform a user calibration (if available): Some V-ZUG ovens allow temperature offset adjustment in the settings menu. Use an oven thermometer to verify actual temperature and adjust within allowed range.

When to call a technician: If the sensor and wiring are correct but F04 remains, the control board's measurement circuit may be defective and requires professional replacement.