La Cornue Induction “U” Flashing on One
La Cornue Induction “U” Flashing on One is a common question among La Cornue owners. This guide walks through it step by step with technician-grade detail.
A flashing “U” on a La Cornue induction zone is the pan-detection indicator: it means the cooktop does not sense a suitable pan on that zone. Often the fix is just the cookware, but sometimes it signals a coil or sensor fault. This guide explains how to tell.
What the “U” means
Induction only heats ferrous (magnetic) cookware placed correctly over the coil. If the pan is missing, too small, off-center, or non-magnetic, the zone shows “U” and won’t heat. This is normal protective behavior, not a fault by itself.
First, check the cookware
- Magnetic test: A fridge magnet should stick firmly to the pan’s base. If it doesn’t, the pan is not induction-compatible.
- Flat bottom: Warped or rounded bottoms break contact. Use flat-bottomed pans.
- Size and centering: The pan base should cover enough of the zone and sit centered over the coil.
See our best induction cookware guide for what works.
The key diagnostic test
Take a pan you know works (it heats fine on another zone) and place it on the problem zone. If a known-good pan still shows “U” on that one zone while other zones heat it normally, the problem is the cooktop — specifically that zone’s induction coil or its sensor — not the cookware.
If it’s a coil or sensor fault
A failed coil or sensor on a single zone is a component-level repair. The rest of the cooktop continues to work, but that zone won’t heat. This requires opening the unit and testing the coil and electronics — see our induction coil replacement guide and the induction repair-or-replace guide.
Other induction codes
A flashing “U” is different from E2 (overheat) or U400 (wiring fault). For those, see our E2 overheating guide and U400 guide.
Professional service
If a known-good pan won’t register on a single zone, schedule an induction diagnostic. Specifications are on lacornueusa.com.
The one test that settles it
Almost every “U” question is answered by a single swap test: take a pan that heats normally on another zone and place it on the problem zone. If that known-good pan heats fine, the original cookware was the issue — wrong material, warped base, or too small or off-center. If the known-good pan still shows “U” on that one zone while other zones heat it, the cooktop is at fault — specifically that zone’s coil or sensor. No tools required, and it tells you immediately whether to change pans or call for service.
Cookware checks before you worry
Run through the basics first: a fridge magnet should cling firmly to the pan’s base (no grip means it is not induction-compatible), the bottom should be flat for full contact, and the pan should be large enough and centered over the coil. A base much smaller than the zone may not be detected at all. Our induction cookware guide covers what works.
Frequently asked
- Is “U” the same as E2 or U400? No — “U” is pan detection, E2 is overheat, U400 is a wiring fault; each has its own guide.
- One dead zone, others fine — repairable? Yes, a single-zone coil or sensor is a component-level repair — see our coil replacement guide.
How the “U” differs from other codes
It helps to keep the induction indicators straight. A flashing “U” is pan detection — the cooktop sees no suitable pan and protects itself by not heating, which is normal. That is different from E2, an overheat warning that clears once the unit cools, and from U400, a wiring fault that shuts the unit off about a second after power-up. Cleaning the glass or changing pans addresses a “U” but does nothing for E2 or U400. Knowing which symptom you have steers you to the right fix rather than the wrong part.
