Why an induction cooktop stops recognising your pan

The cooktop is usually right

Induction is the one cooking surface that regularly gets accused of a fault when it is working perfectly. The call is nearly always some version of: this pan used to work and now the cooktop ignores it.

Before anything else, understand what the appliance is trying to do. A coil under the glass generates an alternating magnetic field. A ferrous pan sitting in that field resists it and heats up. The glass warms only because the pan is on it. If the pan cannot couple with the field, there is nowhere for the energy to go, so the cooktop refuses to switch on rather than dumping power into nothing.

Detection is not the cooktop being fussy. It is the cooktop protecting itself from a situation where it would generate heat with no load to absorb it.

Three ways a pan stops working

It warped. This is the commonest and the most surprising. Pans bow upward in the middle after enough thermal cycling, particularly if they have been heated empty or plunged into cold water while hot. Once the centre lifts, the coupling drops away. The pan may still look flat on the counter — a bow of half a millimetre is enough to matter and is invisible to the eye. Spin the pan on a flat counter: if it rocks or pivots, that is your answer.

It was only partly magnetic to start with. A lot of clad cookware has a thin magnetic disc sandwiched into the base rather than a magnetic body. That works until the disc delaminates or wears, and then the coupling becomes marginal. The symptom is distinctive: the element cycles on and off by itself as detection comes and goes, which looks far more like an appliance fault than a cookware fault.

It is too small for the ring. Detection has a minimum diameter for each element. A small saucepan on a large element will simply not be seen. Move it to a smaller element and it wakes up. People often discover this after rearranging their pans.

The magnet test covers all three cheaply. Press a fridge magnet against the base. It should grab hard, and it should grab everywhere across the bottom, not just in the middle.

When it really is the cooktop

Once the cookware is ruled out, the list gets short.

Thermal cutback, which is the second most common induction call. Everything clever about the appliance lives in a thin space between the glass and the cabinet below, and it is cooled by air moving across it. Block that path — a drawer packed to the top, a filler panel added during a remodel, a stack of baking sheets — and the cooktop pulls its own power back to stay within limits. Owners describe it as an element that loses heat halfway through cooking. It is the appliance defending itself, and in more than a few kitchens the fix is emptying a drawer.

Touch controls that stop responding. Capacitive controls read a film of water or a damp cloth as a finger. If the glass is dry and clean and it still will not respond, we are looking at the control board or its ribbon connection.

Power electronics. Induction cooktops are power electronics with a cooking surface on top, and roughly 68 thunderstorm days a year cross this area. Surge damage tends not to kill a cooktop outright — it produces one element that works intermittently, or a cooktop that runs fine for twenty minutes and then quits, which is easy to confuse with thermal cutback. We check the supply, the airflow and then the boards, in that order.

Before you book

Try the magnet, try a different pan, and check what is directly underneath the cooktop. If those three things do not resolve it, we are an independent shop and the visit is a $129 flat diagnostic credited toward the repair. If the answer turns out to be a warped pan, we will tell you that plainly rather than selling you an inverter board.