OEM Lennox Limit Switch — 69M38

The genuine OEM Lennox 69M38 limit switch is a temperature-sensing safety control that guards your furnace against overheating. Mounted on the heat exchanger or in the plenum, it continuously monitors supply air temperature and opens the burner circuit if the heat rises above the factory-set trip point. This protects the heat exchanger, wiring, and cabinet from thermal damage and is a required component for safe furnace operation.

When the 69M38 wears out or drifts out of calibration, you'll often see short cycling, where the furnace shuts down before satisfying the thermostat, or a complete no-heat condition if the switch has tripped open. A blower that runs nonstop, intermittent lockouts, or repeated ignition attempts are all common indicators that the limit switch is no longer opening and closing at the correct temperatures.

Because this is a safety-critical part, a genuine OEM Lennox switch is the right choice. Aftermarket substitutes may carry the wrong trip rating, leaving your furnace either unprotected or prone to nuisance shutdowns. The factory 69M38 ensures the exact calibration, terminal configuration, and fit needed for safe, dependable heating.