Lennox 57W37 Fan and Limit Control Switch 140-170°F

The Lennox 57W37 (R46105-004) is an automatic limit control switch designed to regulate furnace blower operation and prevent overheating in residential heating systems. This genuine OEM replacement part ensures safe and efficient furnace performance by monitoring heat exchanger temperature.

Key Specifications:

• Actuates (opens) at 170°F to shut off the burner when excessive heat is detected
• Automatically resets at 140°F when temperature returns to safe operating range
• 3-inch insertion depth with green identifying sleeve for easy identification
• Overall assembly length: 3.18 inches
• SPDT (Form C) contact configuration for versatile wiring applications
• Contact rating: 5A at 125VAC for reliable switching performance

Function and Benefits:

This limit switch serves as a critical safety component that turns the furnace blower on and off based on temperature settings while protecting against dangerous overheating conditions. When the heat exchanger reaches the upper limit of 170°F, the switch opens to cut power to the burner, preventing potential damage or safety hazards. Once temperatures drop to 140°F, the switch automatically resets to resume normal operation.

The distinctive green sleeve identifies this as the L170-30F series limit switch, ensuring proper replacement during service. Compatible with select Lennox furnace models, this insertion-style limit control mounts directly into the furnace plenum or heat exchanger for accurate temperature sensing.

Cross-Reference Numbers: R46105-004, L170-30F, 36T01B3