OEM Lennox Limit Switch — 18K69

The genuine OEM Lennox 18K69 limit switch is a critical safety control in your Lennox furnace. It continuously monitors heat exchanger temperature and shuts off the burners if the unit overheats, protecting the heat exchanger and surrounding components from damage. This is a direct factory replacement engineered for exact fit and correct trip temperature in compatible Lennox systems.

Common failure symptoms: When the 18K69 fails, you may notice the furnace short-cycling (heating briefly then shutting off), no heat at all, the blower running continuously, or a burner that ignites but quickly shuts down. A limit switch stuck open will prevent the furnace from firing, while one that fails closed defeats a key safety function.

Why OEM matters: Lennox limit switches are calibrated to precise trip and reset temperatures matched to your specific heat exchanger design. Aftermarket substitutes with the wrong temperature rating can cause nuisance lockouts or, worse, fail to protect against genuine overheating. Choosing the OEM 18K69 ensures your furnace's safety chain works exactly as Lennox designed it, preserving reliable operation and protecting your equipment investment.