Microwave light, fan, and turntable run when the door is closed, even without pressing START.

Safety: This is a serious safety fault. Unplug the Viking microwave immediately and do not use it until repaired.

• Do not operate: A microwave that runs with the door closed but without a command may also energize the magnetron unexpectedly, posing a radiation hazard.
• Inspect door switches: With power disconnected, access the door switch assembly. Check for a switch that is stuck in the closed position or has melted contacts.
• Verify wiring: Compare the wiring to the Viking service diagram (usually inside the cabinet). Correct any miswired connections.
• Replace faulty parts: Replace any defective door switches and, if necessary, the main control board if a relay is stuck closed.
• Professional service recommended: Due to safety implications, have a qualified technician verify proper operation before returning the unit to service.