Oven shows F20; internal temperature rises unexpectedly or remains high even when off.

Safety first: If the oven continues heating uncontrollably, immediately switch off the circuit breaker. Do not use the oven until repaired.

Step-by-step checks:

• Visual inspection of power module: With power off, remove the rear cover and inspect the power PCB for burnt areas near heater relays or triacs.
• Check for stuck relay: If a relay appears melted or discolored, the contacts may be welded closed, causing continuous heating.
• Verify wiring: Ensure no heater wires are incorrectly bridged or connected directly to live after any previous service.
• Replace power module: In most cases, the entire power module should be replaced rather than attempting relay-level repair.

When to call a technician: This is a safety-critical fault. Have an authorized V-ZUG technician replace the defective power module and perform a safety check.