--- title: "Weak or uneven flame" description: "La Cornue weak or uneven flame: a burner that lights cleanly and produces half the heat it used to, or a flame that is tall on one side of the" url: "https://la-cornuemiami.support/symptoms/weak-or-uneven-flame/" date_modified: "2026-09-03" Appliance type: "Cooktops and rangetops, Ranges, Rangetops" --- # La Cornue weak or uneven flame ### Uneven, or weak? Look down onto the lit crown. Flame missing from a section of the ring, or noticeably taller in one place, is a ports-and-cap problem — local, cheap and often a cleaning. A ring that is even all the way round but simply small is a gas-delivery problem: orifice, valve or supply pressure. And check the burner you never use, because a weakening across all of them is easiest to see on the one you have no expectations of. ### What it usually means, by the kind of La Cornue appliance La Cornue sells one appliance in several forms, and the same behavior points at different things on each of them. A built-in side-by-side and an integrated column are not the same service situation, and a dual-fuel range and an induction range fail in different halves. - **Château gas and dual-fuel** — Front burners 17,000 BTU, rears 7,500, power burner 22,000. Knowing which burner is weak tells us what it should be delivering. - **CornuFé 90 and 110 dual fuel** — Five burners on a factory manifold — a single weak one is local, all five is supply. - **Plaque and grill modules** — These are fed by their own burners underneath, so a cold French top or a lukewarm grill is this page rather than a plate problem. ### Why a weak flame is worth a visit on this range and not on a cheap one These burners are the reason somebody bought the range. A 22,000 BTU power burner that has drifted down to something like a domestic hob defeats the point of owning it, and because the loss is gradual the owner adapts — longer to boil, a bigger pan moved to a different burner, a recipe that no longer works. By the time it is described as weak it has usually been weak for a year. It is also nearly always cheap to correct, which is the other reason to look at it. ### Where the real losses hide Two places. The plaque coup de feu is heated by a single 7,500 BTU burner under a solid iron plate, so a weakening burner shows up as a plate that takes longer to come up and has a smaller hot center — described as a plate problem, caused by a burner. And the oven burners on a Château are out of sight entirely, so a rich or restricted oven burner presents as slow cooking rather than as a flame complaint. Both get looked at during a maintenance visit whether or not anyone has complained about them. Partly blocked ports Spill, carbon or corrosion around part of the crown. The classic uneven flame. A cap not seated on its crown Put back slightly off after cleaning. Changes both the shape and the mixture. A restricted orifice Where a burner is even but weak. Small part, immediate difference. A worn or partly blocked valve The knob is fully open and the valve is not. Rebuilt or replaced. Supply pressure below specification Measured at the manifold, and the answer when every burner has faded together. Look down at the crown Even all the way round, or missing in places. That is the diagnosis. Compare with another burner Same size, same setting. A side-by-side comparison beats a memory of how it used to be. Take the cap off and reseat it Free, immediate, and it fixes a fair share of these. Check the plaque and the grill Their burners are out of sight and they weaken unnoticed. It lights, but there is no heat in it What it usually means Uneven around the crown is ports or a misseated cap Weak on every burner is supply pressure or a regulator The plaque burner is the one nobody notices has weakened Uneven, or weak? Look down onto the lit crown. Flame missing from a section of the ring, or noticeably taller in one place, is a ports-and-cap problem — local, cheap and often a cleaning. A ring that is even all the way round but simply small is a gas-delivery problem: orifice, valve or supply pressure. And check the burner you never use, because a weakening across all of them is easiest to see on the one you have no expectations of. What it usually means, by the kind of La Cornue appliance La Cornue sells one appliance in several forms, and the same behavior points at different things on each of them. A built-in side-by-side and an integrated column are not the same service situation, and a dual-fuel range and an induction range fail in different halves. Château gas and dual-fuel — Front burners 17,000 BTU, rears 7,500, power burner 22,000. Knowing which burner is weak tells us what it should be delivering. CornuFé 90 and 110 dual fuel — Five burners on a factory manifold — a single weak one is local, all five is supply. Plaque and grill modules — These are fed by their own burners underneath, so a cold French top or a lukewarm grill is this page rather than a plate problem. Why a weak flame is worth a visit on this range and not on a cheap one These burners are the reason somebody bought the range. A 22,000 BTU power burner that has drifted down to something like a domestic hob defeats the point of owning it, and because the loss is gradual the owner adapts — longer to boil, a bigger pan moved to a different burner, a recipe that no longer works. By the time it is described as weak it has usually been weak for a year. It is also nearly always cheap to correct, which is the other reason to look at it. Where the real losses hide Two places. The plaque coup de feu is heated by a single 7,500 BTU burner under a solid iron plate, so a weakening burner shows up as a plate that takes longer to come up and has a smaller hot center — described as a plate problem, caused by a burner. And the oven burners on a Château are out of sight entirely, so a rich or restricted oven burner presents as slow cooking rather than as a flame complaint. Both get looked at during a maintenance visit whether or not anyone has complained about them. ### Could low pressure be the gas company rather than the range? It can be, and it is measured rather than argued about. We take a reading at the manifold with burners running and compare it to the specification for the fuel the range is set for. If the supply is short, that is a finding we put in writing for you to take to whoever owns the line — and we will not sell you parts to work around it. What is far more common is a regulator at the appliance, or a conversion where the regulator was never changed. ### It got worse after the kitchen was remodelled. Then say so when you book, because it narrows things considerably. A range reconnected with a longer or narrower gas line, a new shut-off valve part-closed, a flexible connector kinked behind the range, or a propane range plumbed into natural gas all produce exactly this and all date from a specific day. We start at the connection rather than at the burner. --- **[Read full article: Weak or uneven flame](https://la-cornuemiami.support/symptoms/weak-or-uneven-flame/)**