Microwave interior light does not come on when the door opens or during cooking, but the unit otherwise works.

Safety first: Disconnect power before replacing the lamp or accessing internal components.

• Step 1 – Access lamp: On many Thermador models, the lamp is accessible by removing a cover on the top or side, or by removing the outer cabinet.
• Step 2 – Inspect bulb: Remove the lamp and visually inspect the filament. Replace with the correct Thermador-specified microwave cavity lamp if burned out.
• Step 3 – Check socket and wiring: Ensure the lamp socket is not burned or loose and that wiring is intact.
• Step 4 – Door switch check: If a new bulb does not light, test the door switches for proper operation, as they often control the light circuit.
• Step 5 – Control board: If switches and lamp are good, the light relay or control board may be faulty and require replacement.

Warning: Use only microwave-rated lamps; incorrect bulbs can overheat.