OEM Lennox Flame Rollout Switch — 15M43

The genuine OEM Lennox 15M43 is a flame rollout switch, a critical safety limit control mounted near the burner assembly of your Lennox gas furnace. Its job is to detect flames or excessive heat that escape ("roll out") from the combustion chamber — a condition caused by blocked flue passages, a cracked heat exchanger, or restricted venting. When triggered, the 15M43 immediately shuts off the gas valve to prevent fire and dangerous combustion conditions.

Common failure symptoms: The furnace lights briefly then shuts down, the blower runs but there is no heat, or the unit locks out on a limit fault. A rollout switch that has tripped due to a genuine fault must be investigated, but the switch itself can also fail open from age, corroded terminals, or repeated thermal cycling and require replacement.

Why OEM matters: Flame rollout switches are calibrated to a specific trip temperature. Installing the exact Lennox 15M43 ensures the safety circuit responds at the manufacturer's rated setpoint — a generic substitute with the wrong temperature rating can nuisance-trip or, worse, fail to protect your equipment and home. Direct factory replacement guarantees correct fit and rated performance for your Lennox system.