One gas burner will not light, or every burner is affected

Turn the control off when a burner does not light normally. Describe what you already observed: no clicking, clicking without ignition, or ignition followed by an unstable flame. Do not keep turning gas on to repeat the observation, and do not use a match as a troubleshooting substitute. A gas odor requires leaving the area and contacting emergency help.

Thermador’s gas-cooktop guidance includes cap placement and dry ignition components among normal owner checks. Only inspect accessible care items after the appliance is off and cool, following the exact manual. If the whole surface is affected, also report a known power interruption or recent service work; do not assume that every igniter failed simultaneously.

A technician needs the symptom pattern and model before deciding what to inspect. Mention whether other range functions were working during the same event and whether cleaning or a spill preceded it. Keep gas valves, internal wiring and burner adjustments out of the owner-check process. A clear history is more helpful than replacing several ignition parts on speculation.

Useful observations before you call

• Identify each affected burner by position, using observations already made.
• State whether the controls, clock or oven also changed behavior.
• Record recent cleaning, a spill, an outage or installation work.

Model-specific reference: Thermador owner support. Features and procedures vary; follow your appliance manual.