OEM Lennox Draft Inducer Limit Switch — 56M66

The genuine OEM Lennox 56M66 draft inducer limit switch is a safety control mounted on or near the draft inducer assembly of your Lennox furnace. It monitors temperature at the inducer and venting path, opening the circuit to shut down operation if excessive heat is detected — a sign of blocked venting, a failing inducer, or restricted combustion airflow. This protects both the inducer motor and the heat exchanger.

Common failure symptoms: A tripped or failed 56M66 can cause the furnace to shut down mid-cycle, prevent the burners from firing, produce intermittent no-heat conditions, or trigger a diagnostic lockout code. A switch that has drifted out of spec may nuisance-trip during normal operation, interrupting comfort even when the system is venting properly.

Why OEM matters: This limit switch is calibrated to the exact trip and reset temperatures required by your Lennox furnace's venting design. Substituting a generic switch with different thresholds risks either bypassing an important safety function or causing repeated false trips. The factory-spec 56M66 delivers correct fitment, accurate temperature response, and the reliable protection engineered into your Lennox equipment.