Thermador induction cooktop not recognising pans

An induction cooktop that beeps and drops a zone is the one fault on this site you have a real chance of solving yourself in ten minutes. It is also the fault most often misread as a dead appliance, because the symptom looks dramatic and the cause is frequently sitting in the cupboard.

Do the one-pan test first

Take a single pan you know works — a heavy magnetic one, base flat, at least as wide as the ring painted on the glass — and run every zone with it in turn. Give each zone a minute at a medium setting.

If that pan works everywhere, the cooktop is fine and your other cookware is the problem. If it fails on one zone and works on the rest, the fault is in that zone’s coil, sensing or power module. If it fails everywhere, look at the supply and the control before anything else. Those three outcomes point in three completely different directions, and the test costs nothing.

A refrigerator magnet stuck firmly to the base of a pan means it will heat. A magnet that clings weakly means the pan will work intermittently, drop out when it gets hot, and drive you to conclude the appliance is faulty. Some tri-ply pans and most stainless pans with a thin magnetic disc behave exactly that way.

Base geometry matters more than people expect

Induction depends on the pan sitting flat and covering enough of the coil. A base that has gone convex from years of heat — a slight dome you can see by laying a straight edge across it — lifts the centre off the glass and reduces coupling. So does a pan whose base is smaller than the zone marking, which is why a small saucepan on a large bridge zone often refuses to latch on.

Heat is the other common cause

Induction electronics live directly under the glass, and they are cooled by a fan drawing air through a vent. If that vent is blocked, or the fan is failing, the cooktop protects itself by shutting a zone down. The tell is timing: the appliance works from cold, runs for fifteen or twenty minutes, then drops zones one after another. Cooking that produces steady high heat brings it on fastest.

Check that nothing stored in the cabinet below is pressed against the vent path, and listen for the fan running during a long boil. A cooktop installed over a warming drawer or a tightly packed cabinet is more likely to run into this than one with clear air below it.

When it is genuinely the appliance

If the one-pan test fails on a single zone with good cookware and clear ventilation, the fault is under the glass — the sensing circuit that decides whether a pan is present, or the power module driving that coil. Modules on these cooktops commonly serve zones in pairs, which is why two adjacent zones sometimes fail together and the rest keep working. That pattern is useful information; note it before you call.

Losing one leg of the 240-volt supply produces a different picture again: the control panel lights and responds normally while no zone will heat at all. If the cooktop went quiet during a storm week, that is where to look first. This county averages around 68 thunderstorm days a year and momentary outages are routine.

What does not cause this

Cleaner residue baked onto the glass is cosmetic. It is not thick enough to lift a pan out of coupling range and it does not interfere with the sensing circuit, so a cooktop that looks marked and works is simply a cooktop that looks marked.

Nor is the cookware’s brand or price relevant, only its base: enough ferrous content for a magnet to hold firmly, a flat contact face, and a diameter that suits the zone. A heavy expensive pan with a warped or largely non-magnetic base will drop out where a cheap flat steel one holds.

Booking

If the one-pan test says the appliance is at fault, the flat $129 diagnostic covers confirming which zone, which component and whether the supply is intact, with a written estimate before any work begins. The diagnostic is credited toward the repair. Parts are genuine OEM, with 90 days on labor and 365 days on parts. Stop using the cooktop and book straight away if the glass is cracked or chipped, or if a zone heats when nothing is set.