OEM Lennox Furnace Limit Switch — 19J81

The genuine OEM Lennox 19J81 limit switch is a temperature-activated safety control for your Lennox gas furnace. Positioned to sense heat exchanger or plenum temperature, it interrupts the gas valve circuit whenever the furnace exceeds its safe operating temperature — guarding against a cracked heat exchanger, overheated components, and the fire hazards that come with an over-firing furnace. It's manufactured to the precise trip point Lennox specifies for the 19J81 application.

Signs of a failing limit switch include a furnace that short-cycles, shuts down prematurely before satisfying the thermostat, repeatedly trips on high limit, or won't light because the switch has failed open. A switch stuck closed is especially dangerous, since it removes the furnace's overheat protection entirely.

Using the OEM 19J81 is essential for safety and reliability. The switch's temperature calibration is matched to your furnace's specific design; an off-spec aftermarket part can nuisance-trip or fail to protect at the correct threshold. Installing the factory limit switch restores dependable heat and proper high-temperature safety.