Lennox 33J38 Limit Switch

The Lennox 33J38 is a high-precision 115-145F auto limit switch engineered to maintain critical thermal safety within residential and commercial HVAC systems. This Normally Closed (N.C.) disc-style control, part of the Lennox 36T series, acts as a primary safety mechanism that monitors heat exchanger temperatures to prevent overheating. Operating on a fixed 115-145 degree Fahrenheit range, the switch is designed to open on temperature rise at 145°F, effectively breaking the circuit to the gas valve or ignition control. Once the system cools to 115°F, the automatic reset feature restores the circuit without requiring manual intervention from a technician. This replacement part is a direct OEM furnace limit switch for a wide range of Lennox, Armstrong, and Ducane equipment, including 80MGF4 and G24M series units. Utilizing a genuine Lennox 33J3801 ensures calibrated trip points and reliable HVAC high limit protection for long-term system stability.

• Automatic Reset Functionality: Eliminates the need for manual resets by automatically closing the circuit once temperatures drop to 115°F.
• Precise Thermal Calibration: Factory-set to open at 145°F and close at 115°F, ensuring exact limit control for HVAC safety.
• Wide Compatibility: Serves as an OEM replacement for Lennox part numbers 33J3801, 1P33J38, and 13687, as well as various Allied and Ducane models.
• Durable Disc-Style Design: Built as a 36T series limit switch to withstand high-cycle thermal stress in heating vestibules.

Is the Lennox 33J38 a manual or auto reset switch?
This is an automatic reset limit switch. It will reset itself once the temperature falls below the 115°F threshold, unlike manual rollout switches that require a physical button press.

What causes a generic furnace limit switch to trip?
Tripping is typically caused by restricted airflow, such as a dirty air filter, a failing blower motor, or internal obstructions in the heat exchanger.

Can this switch be used in cooling applications?
While primarily used in furnace limit control, this normally closed switch is also found in specific air handlers and heat pump configurations requiring thermal regulation between 115°F and 145°F.

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.