OEM Lennox Furnace Limit Switch — 73K17

The genuine OEM Lennox 73K17 is a high-limit safety switch that monitors heat exchanger temperature to keep your Lennox furnace running safely. When temperatures exceed the switch's rated setpoint, the 73K17 opens the control circuit to the burners or gas valve, stopping the heating cycle and preventing damage from overheating; it resets automatically as the system cools. This dependable safety component is used across a broad range of Lennox gas furnaces and air handlers.

Common failure symptoms: A malfunctioning limit switch often shows up as short cycling, no heat, a blower that will not turn off, or a limit-circuit fault reported by the furnace control board. Repeated heating cycles can wear the bimetal sensing element, leading to early tripping or a failure to trip when needed.

Why OEM matters: Each 73K17 is factory-calibrated to a specific trip and reset temperature for your Lennox equipment. An off-spec generic part can cause unsafe operation or false shutdowns. The OEM 73K17 provides the exact temperature calibration, correct terminals, and proper mounting for reliable, safe furnace performance.