Lennox 18K44 Limit Switch

The Lennox 18K44 Limit Switch is a high-reliability OEM replacement normally closed safety control designed for precise thermal management in residential gas furnaces and air handlers. This auto reset limit switch is engineered to maintain system integrity by monitoring internal plenum temperatures. It is calibrated to an open on rise (cut-out) setpoint of 280°F to prevent thermal overload and a close on fall (cut-in) setpoint of 250°F for automatic circuit restoration. As a direct replacement for Lennox 18K4401, this component ensures seamless mechanical and electrical compatibility for contractors servicing Lennox, Armstrong, and Ducane equipment. With a 7-inch insertion length, it provides accurate sensing within the airflow stream, effectively mitigating risks associated with furnace short cycling or restricted airflow. For technicians Troubleshooting HVAC high limit trips, this Lennox furnace safety switch offers the durability required for demanding high-temperature environments, ensuring the blower and gas valve operate within safe parameters.

• Direct OEM Compatibility: Serves as a 1:1 drop-in replacement for the 18K4401, eliminating the need for field modifications.
• Automatic Reset Logic: Features 250-280F AUTO cycling to restore system operation once temperatures return to safe levels.
• Critical Safety Protection: Prevents heat exchanger damage by interrupting the heating circuit at the 280-degree threshold.
• Standardized Fit: 7" probe length ensures proper positioning in the supply plenum for responsive thermal detection.

How do I know if my Lennox 18K44 limit switch is bad?
If the furnace blower runs continuously while the burners stay off, or if the unit is short cycling despite a clean filter, use a multimeter to check for continuity. A failed switch will often remain open even after the system has cooled.

Can I use an 18K4401 to replace an 18K44?
Yes. These parts are technically identical in their thermal specifications, mounting configuration, and electrical ratings.

What causes this high limit switch to trip repeatedly?
Frequent trips are typically caused by restricted airflow. Check for a clogged air filter, blocked return grilles, a dirty evaporator coil, or a failing blower motor before replacing the switch.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.