Mapping the cold zone with bread
Before blaming a part, find out exactly where the heat goes missing. Preheat with the hood closed and every main burner on the same setting, then cover the grates edge to edge with plain slices of white bread. Close the hood for about two minutes on medium and lift it.
The toast is a picture of the fire. A pale stripe front to back in line with one burner points at that burner. A pale band along the front edge on every burner points to the air, the wind or the burner ends. Patchy pale spots scattered all over point to something between the flame and the food, such as grease-clogged heat plates. Photograph the result; it saves a lot of explaining at the visit.
- One pale stripe running front to back: a single burner giving too little.
- Pale along the front or the back only: wind, leveling or the burner ends.
- Scattered pale patches: heat plates, bars or briquettes packed with grease.
- Whole grate pale: a supply problem; see the guide on low and yellow flames.
Why the lid dial can mislead
The dial on the hood measures the air near the top of the hood, often at one end. It can read 450°F while the grate below the cold burner is a hundred degrees cooler. Use it to compare today with last month, not to judge one side against the other.
A single burner that gives less than its neighbors
Blaze lists four signs of spiders or insects nesting in a burner: a gas smell together with yellow flames, a burner that does not reach temperature, a burner that heats unevenly and a burner that makes popping noises. The last three are exactly what a pale toast stripe looks like from the outside. Look along that burner with the grates off; a burner lit only on half its length, or with gaps between the little flames, has blocked ports or a blocked tube.
Rust closes ports too. Stainless and cast burners scale over years of grease, heat and salt air, and a burner with a row of dead ports or a split along its seam is a replacement, not a cleaning job.
A burner sitting crooked after cleaning
Lynx wants burners seated firmly and level with no side-to-side movement, and Napoleon warns that the valve and orifice must enter the burner tube when it goes back in. A burner that is resting on its tab instead of in its bracket can burn weakly, unevenly or out of the tube's mouth. If yours was lifted out recently and the problem started afterward, that is the first suspect.
A burner that only lights from its neighbor
Many grills pass flame from burner to burner through a small channel or bracket. Napoleon names dirty or corroded crossover brackets when burners will not light each other. A burner that never lit at all, while the ones beside it did, leaves a cold stripe that looks like a heat problem but is really an ignition problem.
Source: Blaze — Professional grill instructional book — Symptoms of insect nests: gas smell with yellow flames, burner does not reach temperature, heats unevenly, makes popping noises
Between the flame and the food
Above the burners sit heat plates, flavorizer bars, briquette trays or ceramic radiants. Their job is to spread heat and vaporize drippings. Packed with grease and ash, they block heat in some spots and flare in others; Napoleon lists excessive grease and ash on the sear plates and drip pan, and sear plates put back the wrong way round, among the causes of flare-ups and uneven heat.
Foil does the same thing on purpose. Lynx says no part of the grill should be lined with aluminum foil because it interferes with airflow and causes low heat. A griddle or a big pan covering most of the grate has a similar effect, and Napoleon caps the covered area at 75% of the grill surface.
- Heat plates or bars face the way the manual shows, with the holes and slots where it says.
- No foil on the grates, the plates, the drip tray or the bottom of the firebox.
- Drip tray and grease cup emptied and scraped.
- Plates that are rusted through or sagging over a burner replaced, not flipped.
Source: Lynx — Care & Use / Installation manual — Burners seated firmly and level; no aluminum foil in any part of the grill; an out-of-level grill heats erratically and unevenly, level with a spirit level both ways; wind into the back or the hood gap causes poor performance, use a wind barrier; Napoleon — Built-In Series owner's manual — Valve must enter the burner on reinstall; dirty or corroded cross-light brackets stop burners lighting each other; grease on sear plates and incorrectly installed sear plates cause flare-ups and uneven heat; no more than 75% of the grill surface covered; infrared burner: off, cool 2 minutes, high at least 5 minutes until tiles glow evenly
Where the grill stands and what blows across it
Lynx treats leveling as critical during installation, because a grill out of level burns erratically and heats unevenly, and it asks for a carpenter's spirit level laid front to back and side to side. A cart moved onto a sloping patio for the season needs checking every time it moves; a built-in head in an island is leveled once, by the installer.
Wind is the other half. Lynx warns that wind blowing into the back of a grill or across the gap under the hood can cause poor performance, and it recommends a wind barrier where the grill faces the prevailing breeze. A cold side that always faces the same direction on a breezy afternoon is telling you about the site.
Infrared and pellet grills have their own pattern
A sear burner glowing in patches has grease in the ceramic; Napoleon's cure is to turn it off, let it cool at least two minutes, then run it on high at least five minutes until the tiles glow evenly. On a pellet grill the fire sits in one firepot, so the area directly over it runs hotter by design; a cold zone that suddenly grew larger usually means ash piled in the firepot or a fan that has slowed.
Source: Lynx — Care & Use / Installation manual — Burners seated firmly and level; no aluminum foil in any part of the grill; an out-of-level grill heats erratically and unevenly, level with a spirit level both ways; wind into the back or the hood gap causes poor performance, use a wind barrier
