OEM Lennox Limit Switch — 27K12

The genuine OEM Lennox 27K12 limit switch is a high-limit safety control that protects your Lennox furnace from dangerous overheating. It monitors the temperature at the heat exchanger and instantly de-energizes the burners if the unit exceeds its safe operating range, guarding against the airflow restrictions and blower problems that can crack a heat exchanger or create a fire hazard. This factory component is calibrated to the exact trip point your Lennox system was engineered to use.

Common failure symptoms include repeated short-cycling, loss of heat, a blower motor that never shuts off, or a furnace that locks out and displays a limit-circuit error. A worn or out-of-spec switch will break the control circuit and stop the ignition sequence, leaving your home without heat.

Why OEM matters: The precise trip temperature is what makes a limit switch safe and reliable — aftermarket units often lack correct calibration, leading to false trips or inadequate protection. The Lennox 27K12 meets original factory specifications for temperature threshold, terminal configuration, and mounting, ensuring seamless compatibility and trustworthy safety performance in your Lennox furnace.